ELSEVIER Psychiatry Research 73 (1997) 1-14

PSYCHIATRY

RESEARCH

Serotonin function in human subjects: intercorrelations among central 5HT indices and aggressiveness

Emil F. Coccaro”,“, Richard J. Kavoussia, Robert L. Trestrnanb, Steven M. Gabrielb, Thomas B. Cooper’, Larry J. Sieverb

‘Degatiment of Psychiatry, MCP Hahnemann School of Medicine, 3200 Henry Avenue, Philadelphia, PA 19129, USA Department of Psychiatry, Mt. Sinai School of Medicine, I Gustave L. Ley Place, New York, NYlOO29, USA

‘Analytic Psychopharmacology Laboratory, Nathan Kline Institute, Orangeburg, NY10962, USA

Received 6 February 1997; revised 8 August 1997; accepted 22 August 1997

Abstract

Three central indices of serotonin (5HT) system activity in human subjects were examined to: (a> estimate intercorrelations among 5-HT indices and (b) compare correlations of these indices with a measure of as;aultiveness (Buss-Durkee ‘Assault’) in personality-disordered individuals. Cerebrospinal fluid (CSF) 5hydroxyindoleacetic acid (5HIAA) concentration and prolactin responses to m-chlorophenylpiperazine (m-CPP) m-CPP (PRum-CPP]) and fenfluramine (PRL[FEN]), served as indices of pre-, post- and ‘net’-synaptic central 5-HT activity, respectively. PR~D,L-FEN] responses were inversely related to CSF 5-HIAA concentration and positively correlated with PRum-CPP] responses. Both PRUD,L-FEN] and PRum-CPP] response data correlated equally, and inversely, with BD Buss-Durkee Assault when the same subjects were examined. Basal CSF 5-HIAA concentration did not correlate with Buss-Durkee ‘Assault’. PRL responses to challenge probes which involve activation of 5-HT post-synaptic receptors may correlate better than a basal measure of pre-synaptic 5-HT function with a tendency to assaultive behavior in non-criminally aggressive personality-disordered individuals. 0 1997 Elsevier Science Ireland Ltd.

Keywords: Serotonin; Aggression; Cerebrospinal fluid 5-HIM, Fenfluramine; m-CPP

*Corresponding author. Tel.: + 1 215 8424208; fax: + 1 215 8424321.

0165-1781/97/$17.00 0 1997 Elsevier Science Ireland Ltd. All rights reserved. PIISO165-1781(97)00108-X

2 E.F. Coccaro et al. /PsychiuQ Research 73 (1997) l-14

1. Introduction

Aggressiveness and/or suicidal behavior have been correlated with various indices of central serotonin (5HT) activity in clinical subjects for nearly two decades (Markowitz and Coccaro, 1995). Indices of pre-synaptic 5-HT function, such as cerebrospinal fluid concentrations of the 5-HT metabolite 5-hydroxyindolacetic acid (CSF 5- HIAA) have generally shown inverse correlations with aggressiveness and/or suicidal behavior, suggesting that reduced pre-synaptic output of 5-I-H is etiologically associated with these behav- iors (Brown et al., 1979, 1982; Linnoila et al., 1983; Asberg et al., 1987; Virkkunen et al., 1987, 1994; Limson et al., 1991). In contrast, indices reflective of post-synaptic 5-HT activity (e.g. brain or platelet 5-HT-2a binding) have shown positive correlations with suicidal behavior, suggesting that alterations in post-synaptic (5-I-IT-2a) receptors may also be associated with suicidal behavior (Stanley and Mann, 1983; Mann et al., 1986; Arora and Meltzer, 1989; Biegon et al., 1990; Pandey et al., 1995). Since the net effect of 5-HT central activity in an individual is dependent on both pre-synaptic and post-synaptic activity, in- dices representative of each side of the synapse must be evaluated. Generally, however, clinical studies have not assessed distinct indices of pre- and post-synaptic 5-HT activity in the same sub- jects. Consequently, it has been suggested that an index of net 5-HT activity might better reflect behaviors hypothetically associated with altered 5-HT function (Coccaro et al., 1989).

Indices which reflect the simultaneous con- tributions of both pre- and post-synaptic function have been investigated. One strategy for measur- ing net 5-HT activity is to evaluate hormonal responses to challenge with indirect 5-HT ago- nists. Specifically, L-tryptophan (L-TRYP), 5-hy- droxytryptophan (5-HTP), or fenfluramine (FEN: D- or D&-forms) have been used as indirect 5-HT agonists (Coccaro and Kavoussi, 1994). Indirect agonists enhance synaptic availability of 5-HT which then stimulates post-synaptic receptors leading to an elevation of circulating anterior pituitary hormones. Thus, information regarding both pre-synaptic and post-synaptic S-I-IT activity may be integrated into one measurement. While

theoretically ‘net’ indices should better reflect overall 5-HT activity, studies correlating these indices with aggressive and/or suicidal behavior have yielded conflicting results. For example, cor- tisol responses to 5-HTP challenge (CORflS- HTP]) have been shown to be elevated in mood- disordered patients with history of suicide at- tempt (Meltzer et al., 1984); while prolactin re- sponses to fenfluramine challenge (PRL[D,L- FEN]) appear to be reduced in mood/personal- ity-disordered patients with history of suicide at- tempt (Coccaro et al., 1989; Lopez-Ibor et al., 1990) and to be inversely correlated with mea- sures of aggressiveness, or a history of aggression, in personality-disordered patients in particular (Coccaro et al., 1989, 1996a; O’Keane et al., 1992).

One of the difficulties in interpreting these studies is the limited availability of data regarding how different indices of central 5-HT system ac- tivity are correlated, if at all, with each other. For example, how do ‘pre-synaptic’ 5-HT indices cor- relate with ‘post-synaptic’ indices, and how do these indices intercorrelate with indices thought to reflect aspects of both.

The purpose of this study was to compare three selected, but putatively different, indices of cen- tral 5-HT activity, representative of pre-synaptic, post-synaptic and net-synaptic activity, in a sam- ple of human subjects. Another purpose was to compare the strengths of relationships between each 5-HT index and a measure of aggression in personality-disordered individuals. CSF 5-HIAA concentration was used as a measure of pre-syn- aptic activity (Murphy et al., 1990), prolactin re- sponse to m-chlorophenylpiperazine challenge was used as a measure of post-synaptic 5-HT activity (Kahn and Wetzler, 19911, and prolactin response to D,L-FEN challenge was used as a net measure of pre- and post-synaptic 5-HT activity (Coccaro and Kavoussi, 19941. The primary mea- sure of aggression was the Assault scale from the self-report Buss-Durkee Hostility Inventory (Buss and Durkee, 1957).

2. Methods

2.1. Subjects

The subjects (n = 61) in this report are part of

E.F. Coccaro et al. /Psychiatry Research 73 (1997) 1-14 3

an ongoing investigation regarding the serotoner- gic correlates of mood and personality disorder. Previous publications (Coccaro et al., 1989, 1994a,b) have reported some, but not all, of these data. Subjects were studied at either the Bronx VA Medical Center or the Mt. Sinai Medical Center. Informed consent was obtained prior to study in the manner approved by the Institutional Review Board of the Mt. Sinai School of Medicine and by the Human Studies Subcommittee of the Bronx VA Medical Center. All subjects were given a physical examination, including a medical his- tory, electrocardiogram, blood hematology, chem- istry (including hepatic profile), thyroid function tests, urinalysis and drug screen, and shown to be physically healthy. Medical data were reviewed by a trained internist. Subjects with any evidence of systemic medical illness were excluded before en- try into the study.

Patient subjects had a DSM-III diagnosis of either personality disorder (PD; n = 47) or major affective disorder (MAD; n = 12). Subjects with current or past history of schizophrenia or or- ganic mental syndrome, or a current history of alcoholism or drug abuse/dependence were, as previously described (Coccaro et al., 19891, ex- cluded and not entered into study. Eight of the personality-disordered subjects were female. Ex- clusion of the female subjects did not alter the results of any of the data analyses; accordingly, all analyses include females where present. Because most of the subjects in this report were studied during the DSM-III era, all assigned Axis I and II psychiatric diagnoses are reported according to DSM-III criteria (Spitzer, 1980). Axis I and II disorders were assigned after structured inter- views with the Schedule for Affective Disorders and Schizophrenia - Lifetime Version (Spitzer and Endicott, 1978) and the Structured Interview for the diagnosis of DSM-III Personality Disorder (Stangl et al., 19851, respectively, as previously described (Coccaro et al., 1989). Final diagnoses for both Axis I and II disorders were achieved by consensus of the raters based on the patient interview, review of all available medical records and clinical observation. The mean number of personality disorder diagnoses was 2.3 &- 1.3 per subject (range = 1-6). The frequencies of person-

ality disorder diagnoses by cluster were: (a) dra- matic cluster, n = 26 (histrionic, 12 = 18; border- line, IZ = 16; antisocial, n = 3; narcissistic, II = 2); (b) eccentric cluster, n = 20 (schizotypal, IZ = 18; paranoid, n = 13); (c) anxious cluster, II = 1.5 (ob- sessive-compulsive, n = 9; avoidant, 12 = 6; de- pendent, n = 2; passive-aggressive, n = 2); four subjects met criteria for personality disorder (not otherwise specified). Among the 12 study subjects with major affective disorder, 10 were studied during a major depressive episode, four while in a stable drug-free euthymic state. While two sub- jects were studied twice (once in the depressed state and once in the euthymic state), data from these subjects were only used once in any single analysis. Three normal control subjects (NC) were included in this report because each of these subjects had undergone a D,L-FEN and an m-CPP challenge. These subjects were recruited by ad- vertisement and were determined to be free from any present history, past history, or family history of any major psychiatric disorder.

2.2. General preparation for study

All subjects were instructed to remain drug-free for 2 weeks and to follow a low monoamine diet for at least 3 days prior to study. Females were studied within the first 10 days of the follicular phase of the menstrual cycle.

2.3. Lumbar puncture for CSF 5Hi&I

After an overnight fast and bed rest of at least 8 h, a lumbar puncture was performed in the morning under sterile technique. CSF samples from the 12th to the 16th cc serial aliquots were frozen immediately and stored at - 80°C for later determination of 5-HIAA and homovanillic acid (HVA) by high pressure liquid chromatography with electrochemical detection (Scheinin et al., 1983). Intra- and inter-assay variability were < 3% and < 5%, respectively, for 5-HIAA and < 4% and < 7%, respectively, for HVA.

2.4. Fenfluramine challenge.

D,L-FEN challenge procedures began at 08.00 h

4 E. F. Coccaro et al. /Psychiatry Research 73 (1997) l-14

after an overnight fast. Subjects remained supine, without sleeping, smoking, or eating throughout the procedure from 08.00 h to 15.00 h. Baseline samples for prolactin (PRL) were obtained via an indwelling intravenous catheter at 09.45 h and 09.55 h. Following oral administration of 60 mg D,L-FEN at 10.00 h, samples for plasma PRL were obtained hourly for 5 h. Samples were stored at - 20°C until assay. Plasma PRL was assayed by radioimmunoassay (Davis et al., 1983). Samples for plasma D,L-FEN and its metabolite Nor-D&- FEN were collected hourly in a subgroup of sub- jects and were assayed by gas chromatography- electron detection (GC-ED) with nitrogen-detec- tor .(Krebs et al., 1984). Intra- and inter-assay variability, respectively, were: < 7% and < 9% for PRL and < 7% and < 7% for D&-FEN/Nor-o&- FEN.

Changes in PRL after D,L-FEN administration were calculated by subtracting each post-D&-FEN PRL value from the average baseline PRL value. Peak P~D,L-FEN] values were defined as the maximal PRL response to D,L-FEN during the period when circulating levels of D,L-FEN were ascending, approaching, or at their highest plasma concentration (i.e. t = + 120-300 min after D,L-

FEN administration). This was to ensure that the peak PRIJD,L-FEN] responses reflected the acute pharmacological response to D,L-FEN administra- tion. Peak PR~D,L-FENI values have been found to be highly correlated with area under curve PR~D,L-FEN] values (I = 0.95) (Coccaro et al., 1989).

2.5. m-CPP challenge

m-CPP challenge studies were performed in a similar manner to the D,L-FEN challenge studies. m-CPP (0.5 mg/kg) was administered orally at 10.00 h, and plasma samples for PRL and plasma m-CPP levels were collected every 30 min for 5 h. Plasma m-CPP levels were assayed by GC-ED with nitrogen-detector (Suckow et al., 1990). In- tra- and inter-assay variability for m-CPP levels were < 7% and < 7%.

Changes in PRL after m-CPP administration (PRL[m-CPPI) were calculated by subtracting each post-m-CPP value from the average baseline

PRL value. Peak changes in PRL after m-CPP were defined as the maximal PRL response to m-CPP during the period of highest circulating m-CPP concentration (i.e. within 2 h on either side of the time of the subject’s peak plasma m-CPP concentration). This was to ensure that the peak PRum-CPP] value reflected the acute pharmacological response to m-CPP administra- tion. Peak PRum-CPP] values were correlated with area under the curve (AUC) PRum-CPP] responses (r = 0.73, P < 0.001). Results of analy- ses with AUC PRI_Jm-CPP] responses are also reported where appropriate.

2.6. Behavioral indices: aggression /depression

Aggressiveness was assessed by use of the As- sault scale of the self-report Buss-Durkee Hostil- ity Inventory (BDHI) (Buss and Durkee, 1957). This scale reflects a tendency of the individual to commit a violent assault against another person in response to provocation. A secondary index of aggression used was the Irritability scale of the BDHI. The items on this scale reflect a tendency of the individual to erupt with negative affect and to express exasperation in response to provoca- tion. State depression was assessed as in previous studies using the 21-item Hamilton Depression Rating Scale (HAMD-21) (Guy, 1976).

2.7. Statistical analysis

The primary method of data analysis relied on Pearson product-moment correlations. Differ- ences between correlations, when evaluated, uti- lized the z statistic (Fisher, 1921). Probability values (a = 0.05) are expressed as two-tailed.

3. Results

3.1. Correlation between CSF 5-HL4A concentration and PRLJD,L-FEN] and PRL[m-CPP] responses

Table 1 displays demographic, behavioral and biological data for the subjects in which CSF 5-HIAA concentrations were correlated with PR~D,L-FEN] and PRum-CPP] responses. CSF 5-HIAA and PR~D,L-FEN] data were available

Table I

E. F. Coccaro et al. /Psychiahy Research 73 (1997) I-14

Demographic, behavioral and biological features of comparison samples (mean f S.D.)

Correlation D,L-FEN/CSF m-CPP/CSF (n = 22) (n = 10)

D,L-FEN/m-CPP (n = 22)

Age (years) Weight (kg) Gender (male/female) BDHI ‘Assault’ Hamilton DRS Drug-free period (days) Diagnostic group: (PD/~-Ac/~-Eu/NO

Basal PRUD,L-FEN] (rig/ml) Peak PRL(D,L-FEN] (ng/mll Peak FEN/NorFEN level (rig/ml) Basal PRUm-CPPI (ng/mll Peak PRUm-CPP] (rig/ml) Peak n-CPP level (rig/ml) CSF 5-HIAA (ng/ml) CSF HVA (ng/mll

40.2 (9.8) 81.3 (13.5) (22/O)

6.1 (4.51 17.lC9.41 51.2 (29.71 (16/6/O/O)

5.7 (4.51 9.8 (7.71

82.9 (15.5)

N/A N/A N/A 21.4 (6.5) 38.3 (13.31

in the same individuals in 22 subjects. CSF 5- HIAA concentration and PRI.JD,L-FEN] values were significantly and inversely correlated (r = - 0.56, P = 0.007) in the 22 subjects examined (Fig. 1). Correlation coefficients for PD (r = - 0.50, n = 16, P < 0.05) and MAD-acute sub- jects (r = -0.88, n = 6, P < 0.05) did not differ significantly (z = 1.29, P = 0.174). Like CSF 5- HIAA, CSF HVA concentrations correlated in- versely with PR~D,L-FEN] responses. However, this correlation did not reach statistical signifi- cance (r = - 0.35, tz = 22, P = 0.108). In the 10 subjects in which both PRLEm-CPPI response and CSF 5-HIAA concentration data were available, no significant correlation was noted regardless of whether peak (r = 0.21, P = 0.558) or AUC (r = - 0.08, P = 0.832) PRL[m-CPP] values were used.

3.2. Correlation between PRL[D,L-FEN] and PRL[m-CPP] responses

Table 1 displays demographic, behavioral and biological data for the subjects in which PRLED,L- FEN] and PRum-CPP] responses were corre- lated. PR~D,L-FEN] and PRum-CPP] response data were available in the same individuals in 22 subjects. PR~D,L-FEN] and PRum-CPP] values

36.2 (8.0) 84.5 (13.7)

(10/O) 5.1 (3.3)

12.1 (7.1) 64.4 (33.61 (lo/o/o/o1

N/A N/A N/A

7.7 (3.2) 13.6 (9.3) 26.1 (15.5) 22.4(11.1) 35.3 (1 I .7)

45.8 (11.1) 83.6 (15.8) (22/O) 6.4 (2.3)

14.0 (10.4) 66.8 (31.9) (9/4/4/3)

5.7C4.1) 11.2 (7.7) 80.4 (16.6)

5.9 (2.9) 11.3 (9.5) 35.9 (27.7)

N/A N/A

0 5 10 15 20 25

PRL[d,l-FEN] RESPONSE (nglml)

5

Fig. 1. Correlation between PRUD,L-FEN] responses and basal CSF 5-HIAA concentration in 22 males with mood ( 8) and personality (01 disorders.

were significantly and directly correlated (I = 0.45, n = 22, P = 0.038) in the subjects examined (Fig. 2). The magnitude of this relationship was greatly reduced, however, by the data of one subject who had an exceptionally robust PR~D,L-FEN] value (32.2 ng/ml: 2.7 S.D. above the mean PR~D,L- FEN] value) and a blunted PRIJm-CPP] value (2.5 ng/ml). Reanalysis without this one subject revealed a much stronger relationship between

6 E.F. Coccaro et al. /Psychiatry Research 73 (1997) l-14

4 I I , I I 0 10 20 30

PRL[d.l-FEN] RESPONSE (nglml)

Fig. 2. Correlation between PR~D,L-FEN] and PRUm-CPP] responses in 22 mood (O)/personality (01 disordered and normal control (m) males (dotted line is regression line for correlation without outlier; see text).

PRUD,L-FEN] and PRUm-CPP] values (r = 0.74, IZ = 21, P < .OOl> (Fig. 2).

3.3. Correlation between the central 5-HT indices and BDHI Assault and Irritability

Based on previous work which suggests that aggression may correlate inversely with 5-HT challenge measures in personality-disordered (Coccaro et al., 1989, 1990, 1996a; Moss et al., 1990; O’Keane et al., 19921, but not in major

depressed subjects (Coccaro et al., 1989; Wetzler et al., 19911, correlations between the central 5-HT indices and BDHI ‘Assault’ and ‘Irritability’ were performed only in the personality-dis- ordered (PD) subjects. Table 2 displays demo- graphic, behavioral and biological data for the subjects in which Buss-Durkee Assault and Irri- tability scores were correlated with CSF 5-HIAA and with PR~D,L-FEN] and PRUm-CPP] re- sponses.

BDHI ‘Assault’ scores correlated significantly with PR~D,L-FEN] responses in the PD subjects (r = -0.55, n = 32, P = O.OOl), Fig. 3. Despite the positive correlation between PRUD,L-FEN] and PRL[m-CPP] responses, PRUm-CPP] responses did not correlate as strongly as did PRUD,L-FEN] responses with BDHI Assault (r = -0.32, n = 20, P = 0.163; Fig. 3, top-right) in the total group of m-CPP study subjects. There was no correlation between CSF 5-HIAA concentration and BDHI Assault (r = 0.15, n = 22, P = 0.491; Fig. 3, bot- tom-center) in this sample. Finally, there were no significant correlations between any of these 5-HT variables and BDHI Irritability.

Differences in the strengths of these correla- tions could be due to differences in the individual subject members of the samples. While the sub- samples in which two 5-HT indices were corre- lated with BDHI ‘Assault’ in the same subjects were small, we repeated the correlational analy-

Table 2 Demographic, behavioral and biological features of samples (mean f S.D.) used in correlations with BDHI ‘Assault’

Sample

Age (years) Weight (kg) Gender (male/female): BDHI ‘Assault’ Hamilton DRS Drug-free period (days) Basal PR~D,L-FEN] (ng/ml) Peak PR~D,L-FEN] (ng/ml) Peak FEN/NorFEN level (ng/ml) Basal Pmm-CPP] (ng/ml) Peak PRUm-CPP] (ng/ml) Peak m-CPP level (ng/rnl) CSF 5-HIAA fng/ml) CSF HVA (ng/ml)

D,L-FEN (n = 32)

38.5 (9.4) 79.7 (13.9) (27/5)

5.8 (2.7) 14.4 (7.9) 50.9 (32.3)

6.7 (5.3) 12.lf9.3)

86.3 (12.3) N/A N/A N/A

N/A N/A

m-CPP (n = 20)

39.0 (10.4) 76.6 (15.1) (15/51

5.5 (3.1) 15.4 (7.9) 57.1 (37.8)

N/A N/A N/A

7.6 (3.9) 14.3 (10.0) 26.5 (17.4)

N/A N/A

CSF S-HIAA (n = 22)

37.7 (8.2) 80.4 (13.8) (22/O)

5.6 (2.9) 13.4 (6.2) 53.6 (31.0) N/A N/A N/A N/A N/A N/A 20.5 (5.6) 41.9 (15.7)

E.F. Coccaro et al. /Psychiatry Research 73 (1997) l-14 7

ii 5 20- 5 r=-.56

2 n= 32 . .

4 e IO- 0 .

5 .

1,. ( ., ., , I ,,I 0 2 4 6 6 10

BDHI “ASSAULT”

I,.,.,. 1 ‘, , ( 0 2 4 6 6 10

BDHI “ASSAULT”

r=.l5 .

n = 22 .

p=NS 0

.

5; . , , ( , 1 , , , I 0 2 4 6 a 10

BDHI “ASSAULT”

Fig. 3. Correlation between BDHI ‘Assault’ and top-left: PKUD,L-FEN] responses; top-right: PRUm-CPP] responses; and

bottom-center: CSF 5-HIAA concentrations in male (01 and (01 female personality-disordered subjects.

ses in order to estimate the relative strengths and probes may equally correlate with ‘assaultiveness’ patterns of these relationships in PD subjects in when examined in the same subjects. In contrast, whom: (a) both PRUD,L-FEN] and PRUm-CPP] the subanalysis involving PRL[D,L-FEN] respon- response data (n = 10); and (b) both PRL[D,L- ses and CSF 5-HIAA concentration revealed the FEN] response and CSF 5-HIAA concentration same pattern (i.e. BDHI Assault/PRL[o,r_-FEN] data (rz = 161, were available. The subanalysis in- responses: r = -0.42 and BDHI ‘Assault’/CSF volving PRL responses to D,L-FEN and to m-CPP 5-HIAA concentration: r = 0.12) as observed revealed similar correlation coefficients for the where correlations were derived with data from relationship between BDHI ‘Assault’ and all PD subjects. This result suggests that PRL[D,L- PRUD,L-FEN] (r = -0.56) and PRUm-CPP] (r FEN] responses may be more sensitive than CSF = -0.52). This result suggests that the 5-HT 5-HIAA concentration in detecting inverse rela-

8 E.F. Coccaro et al. /Pychiaty Research 73 (1997) I-14

tionships between assaultiveness and central 5-HT activity. Data with all three 5-HT measures were available in too few subjects to examine the cor- responding intercorrelations with BDHI Assault.

4. Discussion

This study revealed an inverse correlation between PRUD,L-FEN] and CSF 5-HIAA con- centration and a positive correlation between PRL responses to D,L-FEN and m-CPP. Accordingly, these data provide support for the hypothesis that PRIJD,L-FEN] responses represent an integrated, pre-/post-synaptic, index of ‘net’ 5-HT activity in the limbic-hypothalamus. Although PRL[D,L- FEN] responses appeared to more strongly corre- late with ‘assaultiveness’ than PRL[m-CPPI re- sponses, both appeared to correlate equally in subjects in whom PRL response data for both D,L-FEN and m-CPP challenge were available. This is in contrast to the CSF 5-HIAA concentra- tion data where no correlation with BDHI As- sault was found regardless of which subsample of subjects was examined.

4.1. Correlations between central 5-HT indices

The inverse correlation between PRUD,L-FEN] and CSF 5-HIAA concentration suggests that PRUD,L-FEN] responses reflect information from the presynaptic terminal. The inverse correlation may be related to any, or all, of the following: (1) presynaptic turnover of 5-HT; (2) number of functional 5-HT neurons in relevant loci in the central nervous system; or (3) amount of 5-HT available for release by D,L-FEN. Regardless of the precise biological cause of the prolactin re- sponse to D,L-FEN, the directional nature of the correlation in our subjects suggests that PRL[D,L- FEN] responses indirectly reflect pre-synaptic events.

In contrast to our findings, a positive correla- tion between CSF 5-HIAA concentration and PRL[D,L-FEN] response was reported by Mann et al. (1992). Reasons for the difference between our two studies are not readily apparent from exami- nation of the raw biological data. The range of PRUD,L-FEN] responses and CSF 5-HIAA con-

centrations is comparable between the two sam- ples. Hence, the difference cannot lie in the pos- sibility that the data were taken from different sections of a ‘curvilinear’ relationship between these two variables where, for example, the corre- lation might appear to be direct at low PRIJD,L- FEN] response levels and inverse at high PRUD,L-FEN] response levels (or vice versa). It is possible, however, that this difference may be accounted for by important clinical differences in the two samples. First, the Mann et al. (1992) study contained a number of female subjects whom that group has reported as having more robust PRUD,L-FEN] responses than males (Mc- Bride et al., 1990); our sample for this correlation consisted only of males. Second, the former study contained a subgroup of young subjects, 30 years or under, who had markedly robust PRUD,L-FEN1 responses; only one subject in our study was un- der 30 years of age. Third, most of the subjects in the Mann et al. (1992) study were suicide at- tempters with a primary diagnosis of either major or minor depression. Most subjects in our study did not have a history of suicidal attempts (23% vs. 71%, respectively) and the primary diagnosis of most in our study was personality disorder (73%) rather than major/minor depression as in the Mann et al. (1992) study (88%). While there may be substantial coexistence of suicidal behav- ior and aggressive behavior in patients with mood or disorders (Brown et al., 1979, 1982; Coccaro et al., 1989; Lopez-Ibor et al., 19901, it is not known that underlying psychobiological relationships are necessarily the same across different subject populations. For example, inverse relationships between aggression and hormonal response to 5-HT probes have been reported in patients with personality disorders (Coccaro et al., 1989, 1990, 1996a; Moss et al., 1990; O’Keane et al., 19921, but not mood (Coccaro et al., 1989; Wetzler et al., 1991) or panic (Wetzler et al., 1991) disorders. However, despite the differences between these two studies, it should be noted that the data in the study of Mann et al. (19921, and in the study presented herein, are internally consistent. In the former case, suicide attempters have reduced PRIJD,L-FEN] responses (Malone et al., 19961, reduced CSF 5-HIAA concentrations (Mann et

E.F. Coccaro et al. /Psychiatry Research 73 (1997) I-14 9

al., 1996; Mann and Malone, 1997), and a positive correlation between POD-FEN] response and CSF 5-HIAA concentration (Mann et al., 1992). In the latter case personality-disordered subjects have an inverse relationship between physical as- sault and PRL[D,L-FEN] response, a non-signifi- cant positive relationship between physical as- sault and CSF 5-HIAA concentration, and an inverse correlation between PR~D,L-FEN] re- sponse and CSF 5-HIAA concentration.

The inverse relationship between CSF 5-HIAA concentration and PR~D,L-FEN] responses in our subjects does appear to be consistent with inverse correlations reported between CSF 5-HIAA con- centration and hormonal responses to other 5-HT probes in other populations: (a) CORnS-HTP] responses in mood-disordered patients (Koyama et al., 1987); (b) PRum-CPP] responses in low- weight anorectic patients (Brewerton et al., 1990); and (c) PR~D,L-FEN] responses in adolescents with recent history of suicidal behavior (Greenhill et al., 1993). In addition, these data are consistent with animal data which demonstrate enhanced PRIJD,L-FEN] responsiveness 30 days after treat- ment with 5,7-DHT which reduced brain levels of 5-HIAA by 60% (Kuhn et al., 1981). An inverse relationship between PR~D,L-FEN] responses and CSF 5-HIAA concentration is also consistent with the positive correlation between the PRL responses to both D,L-FEN and the direct post- synaptic agonist, m-CPP. Since PR~D,L-FEN] values represent hormonal responses distal to the limbic-hypothalamic 5-HT receptors stimulated by D,L-FEN (Coccaro and Kavoussi, 19941, PR~D,L-FEN] responses should vary as a func- tion of post-synaptic 5-HT receptor responsivity as expressed by PRum-CPP] response.

4.2. Shared variance among the three central 5-HT indices

Unfortunately, too few subjects in this study had simultaneous measures of the three 5-HT indices. Accordingly, the true independent magni- tude of the contribution of basal CSF 5-HIAA concentration and PRL[m-CPP] responses to PR~D,L-FEN] responses cannot be calculated. However, based on the univariate correlations

present, we could estimate that the variance shared by basal CSF 5-HIAA concentration and PR~D,L-FEN] responses may be as much as 31% (r2 = 0.311, while the variance shared by PRum- CPP] and PRIJD,L-FEN] responses may be at least 20% (T’ = 0.20, estimate including outlier subject; r ’ = 0.55 without outlier subject). This leaves a substantial degree of variance in PR~D,L-FEN] responses to be accounted for by other factors unrelated to central 5-I-IT system function not reflected in CSF 5-HIAA or PRum- CPP] measures.

4.3. Correlation between central 5-HT indices and assaultiveness in persona&disordered patients

Since we hypothesized that assaultiveness in personality disordered patients would correlate with integrated 5-HT activity in relevant areas of the central nervous system, we hypothesized that our net index of 5-HT activity, PRLED,L-FEN] response, would more strongly correlate with as- saultiveness than would ‘pure’ indices of either pre- (CSF 5-HIAA) or post- (PRLEm-CPP) synap- tic activity. Our results support this hypothesis only to the extent that 5-HT activity distal to the 5-HT synapse is possibly more critical in defining the relationship between 5-HT activity and ag- gression in these type of subjects. PRL responses to both D,L-FEN and m-CPP challenge demon- strated inverse correlations with BDHI Assault. While only the correlation involving PR~D,L- FEN] response data was statistically significant in the initial analyses, the corresponding correla- tions in the subsample in which each subject had undergone both challenges revealed similar corre- lation coefficients of moderate strength (D,L-FEN: r = - 0.56; m-CPP: r = -0.52). If so, neuronal activity distal to 5-HT neurons may be more critical than pre-synaptic availability of 5-HT in the relationship between 5-HT function and as- saultiveness in these kinds of subjects.

Data from many, though not all, investigations are generally consistent with these findings. In studies conducted in the US (Coccaro et al., 1989, 1996a; Moss et al., 1990; Botchin et al., 1993; Bernstein and Handelsman, 1995; Keys et al., 1995) and abroad (Lopez-Ibor et al., 1990;

10 E.F. Coccaro et al. /Psychiatry Research 73 (1997) I-14

O’Keane et al., 1992), lower PRL responses to o,L-fenfluramine (Coccaro et al., 1989; Lopez-Ibor et al., 1990; Botchin et al., 1993; Keys et al., 1995), o-fenfluramine (O’Keane et al., 1992; Coc- care et al., 1996) and m-CPP (Moss et al., 1990; Bernstein and Handelsman, 1995) are associated with higher aggression scores or a history of overt aggressive behavior in both human (Coccaro et al., 1989, 1996a; Lopez-Ibor et al., 1990; Moss et al., 1990; Botchin et al., 1993; Bernstein and Handelsman, 1995) and non-human primates (Botchin et al., 1993; Keys et al., 1995). The observation that the PRL response to direct pitu- itary lactotroph stimulation is similar in both ag- gressive and non-aggressive personality-dis- ordered subjects (Coccaro et al., 1994b) suggests that these observations reflect an alteration in 5-HT activity which may be localized at least to the limbic-hypothalamus of the central nervous system. It is of note that the three studies which report a positive (Fishbein et al., 1989; Halperin et al., 1994), or no (Staff et al., 1992), relationship between PRUD,L-FEN] response and aggression were conducted in recently drug-dependent sub- jects (Fishbein et al., 1989) or in children/adolescents with disruptive behavioral disorders such as attention deficit/hyperactivity disorder (Staff et al., 1992; Halperin et al., 1994). Reasons for differences among the findings are likely to be due to significant differences in the nature of the samples in terms of drug depen- dence and in developmental factors as related to age (i.e. child vs. adult). Negative results among the few m-CPP studies published may also be related to the nature of the study sample, particu- larly where subjects were mood or anxiety dis- ordered (Wetzler et al,, 1991).

In contrast to much (Brown et al., 1979, 1982; Linnoila et al., 1983; Virkkunen et al., 1987, 1994; Limson et al., 1990, though not all (Gardner et al., 1990; Castellanos et al., 1994; Moller et al., 19961, previous work, basal CSF 5-HIAA concen- tration did not correlate inversely with assaultive- ness in this study. This may be accounted for by significant sample differences between our sub- jects and subject groups in which inverse relation- ships between CSF 5-HIAA concentration and aggression were noted. Subjects in most studies

demonstrating an inverse relationship between basal CSF 5-HIAA concentration and a parame- ter of aggression were more extreme in their aggressive behavior than the subjects in our study. For example, subjects involved in many of these previous studies were either naval recruits dis- charged from service for aggressive behavior (Brown et al., 1979, 1982) or were violent offend- ers (Linnoila et al., 1983; Virkkunen et al., 1994) or impulsive arsonists (Virkkunen et al., 1987, 1994) identified as such while in the criminal justice system because of their crimes. None of the subjects in our clinical sample were involved in the criminal justice system at the time of study, and very few had any history of significant crimi- nal behavior. (Moreover, none of the male veter- ans in this study had received a discharge from the service because of aggressive behavior.) Absence of criminality was also true of another negative CSF 5-HIAA study conducted in border- line personality-disordered subjects (Gardner et al., 1990). In addition, two recent studies, rather than reporting an inverse correlation between aggression and CSF 5-HIAA concentration, re- port a positive correlation in healthy adult volun- teers (Moller et al., 1996) and in attention-deficit disorder children (Castellanos et al., 1994). While the healthy volunteer adults were certainly not severely aggressive, the authors of the second study (Castellanos et al., 1994) suggested a dif- ference in the severity level of aggression as the likely reason for a positive correlation with ag- gression when compared to a previous report (Kruesi et al., 1990) in which an inverse correla- tion between these variables was noted for a different sample studied in the same laboratory.

Given the recent observation of severe blunting of PRIJD-FEN] responses in antisocial violent offenders (O’Keane et al., 1992), it is possible that both pre- and post-synaptic 5-HT function are impaired in aggressive individuals in forensic samples. Reasons for this difference are not known but include the possibility of some devel- opmental failure in the central 5-HT system of the more severely aggressive individuals (Rosen- baum et al., 1994; Whitaker-Azmitia et al., 1994). Our data suggest that the degree of impairment in pre-synaptic 5-HT function, as reflected by

E.F. Coccaro et al. /Psychiahy Research 73 (1997) l-14 11

CSF 5-HIAA concentration, may not be as great in clinical/non-forensic samples. If so, only in- dices reflective of post-synaptic responsivity, which plays a large role in determining the magnitude of 5-HT neurotransmission distal to the 5-HT synapses in question, would correlate with mea- sures of aggression. This suggests further that hormonal responses to 5-HT probes might be more sensitive than basal CSF 5-HIAA concen- tration to detecting significant relationships with aggression in individuals belonging to a less ex- treme, non-criminally aggressive population.

4.4. Receptor-mediated mechanism of PRL, responses to FEN and m-CPP

If post-synaptic 5-HT receptor responsiveness is the key correlate of assaultiveness in non-crimi- nally aggressive individuals, what 5-HT receptor is responsible for the PRL response to D,L-FEN (and m-CPP)? A direct correlation between PRUD,L-FEN] and PRUm-CPP] responses sug- gests the possibility that both agents are working through similar molecular and receptor mecha- nisms in the stimulation of PRL release. Current data suggest that PRL responses to m-CPP are related to activation of 5-HT-2c and 5-HT-la receptors. Among all 5-HT receptors, m-CPP has its greatest affinity (Hoyer et al., 1994) for the 5-HT-2c receptor [note: while affinity for the 5- HT-2a receptors is substantial, m-CPP is a known 5-HT-2a antagonist (Simansky and Schechter, 1988) and cannot stimulate PRL through a 5-HT- 2a receptor mechanism]. The observation that PRUm-CPP] responses are markedly attenuated by the 5-HT-2a/2c antagonist ritanserin (Seibyl et al., 1991) and amesergide (Wang et al., 1995) is consistent with this hypothesis. m-CPP’s affinity for the 5-HT-la receptor is substantial, although an order of magnitude lower than that for the 5-HT-2c receptor. Consistent with this degree of affinity for this receptor, pretreatment with a 5-HT-la antagonist (i.e. pindolol) has been shown to attenuate PRUm-CPP] responses in healthy subjects (Meltzer and Maes, 1995). PRL respon- ses to fenfluramine appear to reflect activation of 5-HT-2c, but not 5-HT-la, receptors. PRL re- sponses to o-fenfluramine can be completely

abolished in the rat (DiRenzo et al., 1989) and human (Goodall et al., 1993) by ritanserin and in the human by the 5-HT-2a/2c antagonist, ame- sergide (Coccaro et al., 1996b). Given the absence of effects of 5-HT-la (pindolol) (Park and Cowen, 19951, 5-HT-2a (amperozide) (Albinsson et al., 1994) and 5-HT-3 (ondansetron) (Coccaro et al., 1996~) antagonists on PRL responses to fenflu- ramine, it is likely that the PRL response to fenfluramine is largely due to activation of lim- bit-hypothalamic 5-HT-2c receptors. Based on our current knowledge of which 5-HT receptor subtypes appear to underlie PRL responses to fenflur&nine and m-CPP, it is possible that the similar inverse relationships observed between as- saultiveness and PRL responses to D&-FEN and to m-CPP (i.e. in the subset of subjects who underwent both D,L-FEN and m-CPP challenge) could be accounted for by a shared variance in 5-HT-2c receptor responsivity.

4.5. Role of limbic-hypothalamic 5-HT-2c receptors in aggression

If PRL responses to fenfluramine reflect dimin- ished responsivity of limbic-hypothalamic 5-HT- 2c receptors, it is possible that 5-HT-2c receptors play a role in aggression (and/or suicidal) behav- ior. However, because studies of the limbic-hypo- thalamic 5-HT-2c receptor in post-mortem brains of suicide victims (or of aggressive individuals) have not been conducted, there is no direct evi- dence to support this hypothesis at this time. On the other hand, increased numbers of 5-HT-2a receptors in frontal cortex have been reported in many studies of post-mortem suicide victims. Is it possible that 5-HT-2c receptors in non-hypo- thalamic areas of the brain are also increased in number? To our knowledge, central 5-HT2c re- ceptor binding is not increased as a function of suicide in either frontal cortex (where there were too few 5-HT-2c receptors to detect) or hip- pocampus in post-mortem studies of suicide vic- tims (J.J. Mann, personal communication, 1997). Receptor number, as reflected by binding studies, does not necessarily correlate with receptor sensi- tivity, however. For example, despite the observa- tion of increased numbers of 5-HT-2a receptors

12 E.F. Coccaro et al. /Psychiatry Research 73 (1997) l-14

on platelets of suicidal individuals (Pandey et al., 1995), physiological responses of platelet 5-HT-2a receptors have been shown to have impaired sig- nal transduction in suicidal depressed patients (McBride et al., 1994). Accordingly, even if 5-HT- 2c receptor numbers are not altered in certain brain regions of suicide vicitims, unpaired signal transduction, as reflected by reduced PRL re- sponses to D,L-FEN (or m-CPP), may in fact be present in aggressive, and/or suicidal, individuals.

5. Conclusion

Our results suggest that PRL responses to D,L-

FEN (and probably m-CPP) correlate inversely with a tendency towards assaultive behavior, and may do so with greater sensitivity than basal CSF 5-HIAA concentration, in non-criminally aggres- sive personality-disordered patients. We do not suggest, however, that PRL responses to 5-HT probes can fully account for the 5-HT component that might be related to the tendency towards aggressive behavior in these individuals. One, PRUD,L-FEN] responses may only reflect a sub- set of 5-HT (e.g. 2c subtype) receptor systems. Two, these responses may not reflect 5-HT activ- ity in relevant areas of the brain beyond the limbic-hypothalamus. While the magnitude of the role of altered 5-HT processes in impulsive-ag- gressive behavior is not known at the present time, we would suggest, based on existing data from univariate correlations, that 5-HT processes underlying PRUD,L-FEN] responses are likely to account for no more, and probably less, than 30% of the variance in aggressive behavior in personal- ity-disordered individuals assessed by self-report questionnaire.

References

Albinsson, A., Palazidou, E., Stephenson, J., Andersson, G., 1994. Involvement of the 5-HT-2 receptor in the 5-HT receptor-mediated stimulation of prolactin release. Euro- pean Journal of Pharmacology 251, 157-161.

Arora, R.C., Meltzer, H.Y., 1989. Serotonergic measures in the brains of suicide victims: 5-HT-2 binding sites in the frontal cortex of suicide victims and control subjects. Amer- ican Journal of Psychiatry 146, 730-736.

&berg, M., Schalling, D., Triiskman-Bendz, L., Wagner, A., 1987. Psychobiology of suicide, impulsivity and related

phenomena. In: Meltzer, H.Y. (Ed.), Psychopharmacology: Third Generation of Progress, Raven Press, New York, pp. 655-688.

Bernstein, D.P., Handelsman, L., 1995. The neurobiology of substance abuse and personality disorders. In: Ratey, J.J. (Ed.), Neuropsychiatry of Personality Disorders. Blackwell Science, Cambridge, MA., pp. 120-148.

Biegon, A., Grinspoon, A., Blumenfeld, B.A., Apter, A., Mester, R., 1990. Increased serotonin 5-I-IT, receptor bind- ing on blood platelets of suicidal men. Psychopharmacology 100, 165-167.

Botchin, M.B., Kaplan, J.R., Manuck, S.B., Mann, J.J., 1993. Low versus high prolactin responders to fenfluramine chal- lenge: marker of behavioral differences in adult male cyn- molgus macaques. Neuropsychopharmacology 9, 93-99.

Brewerton, T.D., Brandt, H.A., Lessem, M.D., Murphy, D.L., Jimerson, D.C., 1990. Serotonin in eating disorders. In: Coccaro, E.F., Murphy, D.L. (Eds.), Serotonin in Major Psychiatric Disorders. American Psychiatric Press, Wash- ington, DC., pp. 153-184.

Brown, G.L., Goodwin, F.K., Ballenger, J.C., Goyer, P.F., Major, L.F., 1979. Aggression in humans correlates with cerebrospinal fluid amine metabolites. Psychiatry Research 1, 131-139.

Brown, G.L., Ebert, M.H., Goyer, P.F., Jimerson, D.C., Klein, W.J., Bunney, W.E., Goodwin, F.K., 1982. Aggression, sui- cide and serotonin: relationships to CSF amine metabolites. American Journal of Psychiatry 139, 741-746.

Buss, A.H., Durkee, A., 1957. An inventory for assessing different kinds of hostility. Journal of Consulting Psy- chology 21,343-348.

Castellanos, F.X., Elia, J., Kruesi, M.J.P., Gulotta, C.S., Mef- ford, I.N., Potter, W.Z., Ritchie, G.F., Rapoport, J.L., 1994. Cerebrospinal fluid monoamine metabolites in boys with attention deficit hyperactivity disorder. Psychiatry Research 52, 305-316.

Coccaro, E.F., Kavoussi, R.J., 1994. The neuropsychopharma- cologic challenge in biological psychiatry. Clinical Chem- istry 40, 319-327.

Coccaro, E.F., Siever, L.J., Klar, H., Maurer, G., Cochrane, K., Cooper, T.B., Mohs, R.C., Davis, K.L., 1989. Serotonergic studies in affective and personality disorder patients: corre- lates with suicidal and impulsive aggressive behavior. Archives of General Psychiatry 46,587-599.

Coccaro, E.F., Gabriel, S., Siever, L.J., 1990. Buspirone chal- lenge: preliminary evidence for a role for central 5-HT-la receptor function in impulsive aggressive behavior in hu- mans. Psychopharmacology Bulletin 26, 393-405.

Coccaro, E.F., Silverman, J., Klar, H.M., Horvath, T.B., Siever, L.J., 1994a. Familial correlates of reduced central seroton- ergic system function in patients with personality disorder. Archives of General Psychiatry 51, 318-324.

Coccaro, E.F., Klar, H.M., Siever, L.J., 1994b. Reduced pro- lactin response to fenfluramine challenge in personality disorder patients is not due to deficiency of pituitary lac- totrophs. Biological Psychiatry 36, 344346.

E.F. Coccaro et al. /Psychiahy Research 73 (1997) I-14 13

Coccaro, E.F., Kavoussi, R.J., Berman, M.E., Hauger, R.L., 1996a. Relationship of prolactin response to d-fenfluramine to behavioral and questionnaire assessments of aggression in personality disordered males. Biological Psychiatry 40, 157-164.

Coccaro, E.F., Kavoussi, R.J., Oakes, M., Hauger, R.L., 1996b. Amesergide completely blocks the prolactin response to d-fenfluramine in healthy male subjects. Psychopharma- cology 126, 24-30.

Coccaro, E.F., Kavoussi, R.J., Cooper, T.B., Hauger, R.L., 1996~. 5-HT-3 receptor antagonism by ondansetron does not attenuate the prolactin response to d-fenfluramine challenge in healthy male subjects. Psychopharmacology 127, 108-112.

Davis, B.M., Mathe, A.A., Mohs, R.C., Levy, MI., 1983. Ef- fects of probantheline bromide on basal growth hormone, cortisol and prolactin levels. Psychoneuroendocrinology 8, 103-107.

DiRenzo, Cl., Amoroso, S., Taglialatela, M., Canzoniero, L., Basile, V., Fatatis, A., 1989. Pharmacological characteriza- tion of serotonin receptors involved in the control of pro- lactin secretion. European Journal of Pharmacology 162, 371-373.

Fishbein, D.H., Lozovsky, D., Jaffe, J.H., 1989. Impulsivity, aggression and neuroendocrine responses to serotonergic stimulation in substance abusers. Biological Psychiatry 25, 1049-1066.

Fisher, R.A., 1921. On the probable error of a coefficient of a correlation deduced from a small sample. Metron 1, 3-32.

Gardner, D.L., Lucas, P.B., Cowdry, R.W., 1990. CSF metabolites in borderline personality disorder compared with normal controls. Biological Psychiatry 28, 247-254.

Goodall, E.M., Cowan, P.J., Franklin, M., Silverstone, T., 1993. Ritanserin attenuates anorectic, endocrine and thermal responses to d-fenfluramine in human volunteers. Psy- chopharmacology 112,461-466.

Greenhill, L.L., Stanley, M., Schaffer, D., 1993. Prolactin responses to d,l-fenfluramine in suicidal, depressed adoles- cents. Biological Psychiatry 33, 64A.

Guy, W., 1976. ECDEU Manual for Psychopharmacology. (USDHEW publication ADM 76-338). Superintendent of Documents, US Government Printing Office, Washington, D.C.

Halperin, J.M., Sharma, V., Siever, L.J., Schwartz, S.T., Matier, K., Wornell, G., Newcorn, J.H., 1994. Serotonergic function in aggressive and nonaggressive boys with attention deficit hyperactivity disorder. American Journal of Psychiatry 151, 2433248.

Hoyer, D., Clarke, D.E., Fozard, J.R., Hartig, P.R., Martin, G.R., Mylecharane, E.J., Saxena, P.R., Humphrey, P.P.A., 1994. VII. International Union of Pharmacology classifica- tion of receptors for 5-hydroxytryptamine (serotonin). Pharmacological Reviews 46, 158-203.

Kahn, R.S., Wetzler, S., 1991. m-Chlorophenylpiperazine as a probe of serotonergic function. Biological Psychiatry 30, 1139-l 166.

Keys, R.C., Botchin, M.B., Kaplan, J.R., Manuck, S.B., Mann, J.J., 1995. Aggression and brain serotonergic responsivity: response to slides in male macaques. Physiology and Be- havior 57, 205-208.

Koyama, T., Lowy, M.T., Meltzer, H.Y., 1987. 5-Hydroxytryp tophan-induced cortisol response and CSF 5-HIAA in de- pressed patients. American Journal of Psychiatry 144, 334-337.

Krebs, H.A., Chens, L.K., Wright, G.J., 1984. Determination of fenfluramine and norfenfluramine in plasma using a nitrogen-sensitive detector. Journal of Chromatography 310, 412-417.

Kruesi, M.J.P., Rapoport, J.L., Hamberger, S., Hibbs, E., Pot- ter, W.Z., Lenane, M., Brown, G.L., 1990. Cerebrospinal fluid metabolites, aggression and impulsivity in disruptive behavior disorders of children and adolescents. Archives of General Psychiatry 47, 419-462.

Kuhn, C.M., Vogel, R.A., Mailman, R.B., Mueller, R.A., Schanberg, SM., Breese, G.R., 1981. Effect of 5,7-dihy- droxytryptamine on serotonergic control of prolactin secre- tion and behavior in rats. Psychopharmacology 73, 188-193.

Limson, R., Goldman, D., Roy, A., Lamparski, D., Ravitz, B., Adinoff, B., Linnoila, M., 1991. Personality and cere- brospinal fluid monoamine metabolites in alcoholics and controls. Archives of General Psychiatry 48, 4.37-441.

Linnoila, M., Virkkunen, M., Scheinin, M., Nuutila, A., Ri- mon, R., Goodwin, F.K., 1983. Low cerebrospinal fluid 5-hydroxyindolacetic acid concentration differentiates im- pulsive from nonimpulsive violent behavior. Life Sciences 33, 2609-2614.

Lopez-Ibor, J.J., Lana, F., Saiz Ruiz, J., 1990. Conductas autoliticas impulsivas y serotonina. Actas Luso-Espanolas de Neurologia y Psiquiatria 18, 316-325.

Malone, K.M., Corbitt, E.M., Li, S., Mann, J.J., 1996. Prolactin response to fenfluramine and suicide attempt lethality in major depression. British Journal of Psychiatry 168, 324-329.

Mann, J.J., Stanley, M., McBride, P.A., McEwen, B.S., 1986. Increased serotonin-2 and beta-adrenergic receptor binding in the frontal cortices of suicide victims. Archives of Gen- eral Psychiatry 43, 9544959.

Mann, J.J., McBride, P.A., Brown, R.P., Linnoila, M., Leon, AC., DeMeo, M., Mieczkowski, T., Meyers, J.E., Stanley, M., 1992. The relationship between central and peripheral serotonin indices in depressed and suicidal psychiatric in- patients. Archives of General Psychiatry 49, 442-446.

Mann, J.J., Malone, K.M., 1997. Cerebrospinal fluid amines and higher-lethality suicide attempts to depressed in- patients. Biological Psychiatry 41, 162-171.

Markowitz, P.I., Coccaro, E.F., 1995. Biological challenge studies of impulsivity, aggression and suicidal behavior. In: Stein, D., Hollander, E. (Eds.1, Impulsive Aggression and Disorders of Impulse Control. J. Wiley, Sussex.

McBride, P.A., Tierney, H., DeMeo, M.. Chen, J.-S., Mann, J.J., 1990. Effects of age and gender on CNS serotonergic responsivity in normal adults. Biological Psychiatry 227, 1143-1155.

14 E.F. Coccaro et al. /Psychiatry Research 73 (1997) 1-14

McBride, P.A., Brown, R.P., DeMeo, M., Keilp, J., Mieczkowski, T., Mann, J., 1994. The relationship of platelet .5-I-IT2 receptor indices to major depressive disorder, perso- nality traits and suicidal behavior. Biological Psychiatry 35, 29.5-308.

Meltzer, H.Y., Maes, M., 1995. Pindolol pretreatment blocks stimulation by meta-chlorophenylpiperazine of prolactin but not cortisol secretion in normal men. Psychiatry Re- search 58, 89-98.

Meltzer, H.Y., Perline, R., Tricou, B.J., Lowy, M.T., Robert- son, A., 1984. Effect of 5-hydroxytryptophan on serum cortisol levels in major affective disorders. II. Relation to suicide, psychosis, and depressive symptoms. Archives of General Psychiatry 41, 379-387.

Moller, SE., Mortensen, EL, Breum, L., Alling, C., Larsen, O.G., Boge-Rasmussen, T., Jensen, C., Bennicke, K., 1996. Aggression and personality: Association with amino acids and monoamine metabolites. Psychological Medicine 26, 323-331.

Moss, H.B., Yao, J.K., Panzak, G.L., 1990. Serotonergic re- sponsivity and behavioral dimensions in antisocial personal- ity disorder with substance abuse. Biological Psychiatry 28, 325-338.

Murphy, D.L., Mellow, A.M., Sunderland, T., Aulakh, C.S., Lawlor, B.L., Zohar, J., 1990. Strategies for the study of serotonin in humans. In: Coccaro, E.F., Murphy, D.L. (Eds.), Serotonin in Major Psychiatric Disorders. American Psychiatric Press, Washington, D.C., pp. 3-25.

G’Keane, V., Moloney, E., O’Neill, H., O’Connor, A., Smith, C., Dinan, T.G., 1992. Blunted prolactin responses to d- fenfluramine in sociopathy: evidence for subsensitivity of central serotonergic function. British Journal of Psychiatry 160,643-646.

Pandey, G.N., Pandey, S.C., Dwivedi, Y., Sharma, R.P., Jani- cak, P.G., Davis, J.D., 1995. Platelet 5-HT-2a receptors: a potential biological marker for suicidal behavior. American Journal of Psychiatry 152, 850-855.

Park, S.B.G., Cowen, P.J., 1995. Effect of pindolol on the prolactin response to d-fenfluramine. Psychopharmacology 118, 471-474.

Rosenbaum, L.A., Coplan, J.D., Friedman, S., Bassoff, T., Gorman, J.M., Andrews, M.W., 1994. Adverse early experi- ences affect noradrenergic and serotonergic functioning in adult primates. Biological Psychiatry 35, 221-227.

Scheinin, M., Chang, W.-H., Kirk, K.L., Linnoila, M., 1983. Simultaneous determination of 3-methoxy-4-hydroxyphen- ylglycol, 5-hydrovindoleacetic acid, and homovanillic acid in cerebrospinal fluid with high-performance liquid chro- matography using electrochemical detection. Analytical Biochemistry 131, 246-253.

Seibyl, J.P., Krystal, J.H., Price, L.H., Woods, S.W., D’Amico, C., Heninger, G.R., Chamey, D.S., 1991. Effects of ritan-

serin on the behavioral, neuroendocrine and cardiovascular response to meta-chlorophenylpiperazine in healthy human subjects. Psychiatry Research 38, 227-236.

Simansky, K.J., Schechter, L.E., 1988. Properties of some l-arylpiperazines as antagonists of stereotyped behaviors mediated by central serotonergic receptors in rodents. Journal of Pharmacology and Experimental Therapeutics 247, 1073-1081.

Spitzer, R.L., 1980. The Diagnostic and Statistical Manual, 3rd ed., Revised (DSM-III). American Psychiatric Press, Wash- ington, DC.

Spitzer, R.L., Endicott, J., 1978. Schedule for Affective Dis- orders and Schizophrenia. NY State Psychiatric Institute, New York.

Stangl, D., Pfohl, B., Zimmerman, M., 1985. Structured inter- view for DSM-III personality disorder. Archives of General Psychiatry 42, 591-598.

Stanley, M., Mann, J.J., 1983. Increased serotonin-2 binding sites in frontal cortex of suicide victims. Lancet 1, 214-216.

Stoff, D.M., Pastiempo, A.P., Yeung, J.H., Cooper, T.B., Bridger, W.H., Rabinovich, H., 1992. Neuroendocrine re- sponses to challenge with d,l-fenfluramine and aggression in disruptive behavior disorders of children and adoles- cents. Psychiatry Research 43, 263-276.

Suckow, R.F., Cooper, T.B., Kahn, R.S., 1990. High perfor- mance liquid chromatography method for the analysis of plasma m-chlorophenylpiperazine. Journal of Chromatog- raphy 528,228-234.

Virkkunen, M., Nuutila, A., Goodwin, F.K., Linnoila, M., 1987. Cerebrospinal fluid metabolite levels in male arson- ists. Archives of General Psychiatry 44, 241-247.

Virkkunen, M., Rawlings, R., Tokola, R., Poland, R.E., Guidotti, A., Nemeroff, C., Bissette, G., Kalogeras, K., Karonen, S.L., Linnoila, M., 1994. CSF biochemistries, glu- cose metabolism, and diurnal activity rhythms in alcoholic, violent offenders, fire setters and healthy volunteers. Archives of General Psychiatry 51, 20-27.

Wetzler, S., Kahn, R.S., Asnis, G.M., Kom, M., van Praag, H.M., 1991. Serotonin receptor sensitivity and aggression. Psychiatry Research 37, 271-279.

Whitaker-Azmitia, P.M., Zhang, X., Clarke, C., 1994. Effects of gestational exposure to monoamine oxidase inhibitors in rats: preliminary behavioral and neurochemical studies. Neuropsychopharmacology 11, 125-132.

Wong, C.M., DeCaria, C.M., Hollander, E., 1995. Amesergide pretreatment of m-CPP in normal controls. Proceedings of the 34th Annual Scientific Meeting of the American Col- lege of Neuropsychopharmacology, San Juan, Puerto Rico, p. 126.