Comparison of cerebrospinal fluid monoamine metabolite levels in dominant-aggressive and non-aggressive dogs

Aggression has been shown to be related to reduced serotonergic activity in humans and non-human primates, and in rodents. We now studied the relationship between cerebrospinal fluid (CSF) monoamine metabolites and canine aggression in 21 dominant-aggressive dogs (Canis familiaris) and 19 controls. The diagnosis of dominance-related aggression was based upon a history of biting family members in contexts associated with dominance challenges. Post-mortem CSF 5-HIAA, MHPG and HVA were measured by high-performance liquid chromatography using electrochemical detection. Concentrations of CSF 5-HIAA (P = 0.01) and HVA (P < 0.001) were lower in the aggressive group (median values: 5-HIAA 202.0 pmol/ml; HVA 318.0 pmol/ml) than in controls (5-HIAA 298.0 pmol/ml; HVA 552.0 pmol/ml). No differences were noted in CSF MHPG levels. Differences in 5-HIAA were maintained after controlling for breed and age of dogs, but HVA differences may have been breed-dependent. Lower levels of 5-HIAA (P = 0.02) and HVA (P = 0.04) were found in the subgroup of aggressive dogs with a history of biting without warning (5-HIAA 196.0 pmol/ml; HVA 302.0 pmol/ml) compared to dogs that warned (5-HIAA 244.0 pmol/ml; HVA 400.0 pmol/ml). This study suggests that reduced serotonergic function is associated with aggressive behavior and impaired impulse control in dogs, a finding that is consistent with observations in primates, and suggests that serotonin modulates aggressive behavior throughout mammals.

Prolactin response to fenfluramine and suicide attempt lethality in major depression

BACKGROUND

This study employed an alternative method for assessing serotonergic function to further evaluate our finding that cerebrospinal fluid (CSF) 5-hydroxyindole acetic acid (5-HIAA) in depressed suicide attempters with a lifetime history of higher lethality suicide attempts is significantly lower compared to depressed patients who have a history of low lethality suicide attempts.

METHOD

We used dl-fenfluramine (60 mg) as a neuroendocrine probe to examine the serotonin system in 41 in-patients with a DSM-III-R major depressive episode, divided into two groups on the basis of a lifetime history of high or low lethality suicide attempts. Fenfluramine challenge test outcome was defined as the maximum prolactin response in the five hours following fenfluramine.

RESULTS

Patients with a history of a higher lethality suicide attempt had a significantly lower prolactin response to fenfluramine, even when controlling for cortisol, age, sex, weight, comorbid cluster B personality disorder, pharmacokinetic and menstrual cycle effects.

CONCLUSIONS

The data provide further support for the hypothesis that serotonin dysfunction is associated with more lethal suicide attempts, and suggests that higher lethality suicide attempters or failed suicides resemble completed suicides both behaviourally and biochemically.

Demonstration in vivo of reduced serotonin responsivity in the brain of untreated depressed patients

OBJECTIVE

For over 25 years, it has been hypothesized that major depression is due to a deficiency of available serotonin or subsensitivity of key serotonin receptors in relevant brain regions. Direct evidence supporting this hypothesis has been lacking because of the difficulty in studying regional brain serotonergic function. The authors have developed a method for visualizing in vivo regional brain responses to serotonin release by comparing regional brain glucose metabolism after administration of the serotonin-releasing drug dl-fenfluramine, relative to placebo.

METHOD

Results with healthy subjects (N = 6) were compared to those obtained with drug-free inpatients with moderately severe major depression (N = 6).

RESULTS

Healthy subjects had several areas of statistically significant increases in metabolism, mostly in the left prefrontal and temporoparietal cortex, and areas of decreased metabolism, such as in the right prefrontal cortex. In contrast, the depressed patients had no areas of increase or decrease in metabolism, differing significantly from healthy subjects. Results with patients resembled those with healthy subjects (N = 10) who were scanned twice without active drug on either occasion.

CONCLUSIONS

This study provides the first direct visualization of blunted regional brain responses to serotonin release in the brain of patients with major depression, a finding that supports the hypothesis of impaired serotonergic transmission in depression.

Fewer pigmented locus coeruleus neurons in suicide victims: preliminary results

Studies of the noradrenergic system in suicide victims have found evidence of alterations in cortical beta- and alpha-adrenergic receptor binding. Since these receptor changes may be secondary to altered noradrenergic input, we sought to determine whether the pigmented neurons of the locus coeruleus (LC), which provide the noradrenergic innervation to the cerebral cortex, are altered in suicide victims. We studied 11 controls without known psychiatric or neurologic disorders and six suicide victims. LC neuron number, LC volume, and neuron density were determined by computer-assisted mapping. The suicide group had 23% fewer LC neurons and a 38% lower density of LC neurons than controls. The reduction in neuron number was localized to the rostral two thirds of the LC. Neither the LC length nor the LC volume in suicide victims differed from controls. Altered brain noradrenergic neurotransmission in suicide victims may be due to fewer noradrenergic neurons in the LC. Further studies are needed to determine whether this noradrenergic neuron loss is associated with an underlying major depression or specifically with suicidal behavior.

Lower 3H-paroxetine binding in cerebral cortex of suicide victims is partly due to fewer high affinity, non-transporter sites

Suicide has been associated with decreased serotonin transmission. Measurement of concentrations of serotonin, its precursors tryptophan (TRY) and 5-hydroxytryptophan (5-HTP) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA), have been used as indices of serotonin activity, and with serotonin transporter binding, are indices of the integrity of serotonin nerve terminals. Most previous studies have not distinguished high affinity transporter binding from a very similar nontransporter binding site, where binding is not dependent on Na+ or Cl- and that does not have a known functional role. We therefore, assayed binding kinetics in prefrontal (PFC) and temporal cortex (TC) in matched pairs of suicide victims and controls using the selective ligand 3H-paroxetine, and employing 1 microM sertraline to define specific binding to the transporter and 10 microM sertraline which also displaces binding to the high affinity, nontransporter site. In addition, we measured concentrations of TRY, 5-HTP, serotonin and 5-HIAA in the same brain areas. The total number of 3H-paroxetine transporter and nontransporter binding sites (Bmax), was lower in the suicide group compared to controls in both Brodmann area 9 (prefrontal cortex; p = 0.02) and in Brodmann area 38 (temporal cortex, p = 0.01). In contrast, no differences were found in the number of high affinity transporter binding sites and concentrations of serotonin, 5-HIAA, 5-HTP or TRY (p > 0.05). We conclude that the number of serotonin transporter sites is not altered in Brodmann area 9 in suicide, and that fewer 3H-paroxetine and 3H-imipramine binding sites found in this region of cerebral cortex of suicides may be explained by a reduction in the nontransporter binding sites.

Serotonin 5-HT3 receptor binding kinetics in the cortex of suicide victims are normal

Serotonergic abnormalities have been identified in the brain of suicide victims independent of psychiatric diagnosis. We report the first study of serotonin 5-HT3 receptors in the brain of suicide victims. There were no differences in the number (Bmax) or affinity (KD) of 5-HT3 receptors in the temporal cortex of suicide victims compared to matched controls. There was a negative correlation between brain serotonin levels and receptor number (r = -0.5, p = 0.04) in both groups. This study indicates that alterations in serotonergic function in the brain of suicide victims do not appear to directly involve the 5-HT3 receptor.

Long-term effects of chronic social stress on serotonergic indices in the prefrontal cortex of adult male cynomolgus macaques

We examined the effects of chronic social stress and social rank on monamine concentrations in the prefrontal cortex (PFC) in adult male cynomolgus macaques (Macaca fascicularis). Seventy-five animals were housed in five-member social groups for 28 months and were exposed to three experimental conditions. A 'no-stress' condition was comprised of animals housed in groups of stable membership throughout the study. Animals assigned to a 'past-stress' condition had their group memberships reorganized at monthly intervals during the first (but not last) 14 months of the study, and a third 'recent-stress' condition consisted of social groups reorganized only during the last 14 months. At necropsy, the brains were collected and frozen at -70 degrees C until analyzed. Prefrontal orbital cortex was assayed for monoamines (serotonin (5-HT), dopamine (DA), norepinephrine (NE)), metabolites (5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), 3-methoxy-4-hydroxyphenethyleneglycol (MHPG)), and tryptophan using high-performance liquid chromatography with electrochemical detection. Animals in the past-stress condition had significantly lower PFC 5-HIAA concentrations compared to those in the no-stress condition (P < 0.05). PFC 5-HT concentrations of animals in the past-stress condition were significantly lower than those in the no-stress and recent-stress conditions (P < 0.01). The concentrations of DA, HVA, NE and MHPG were not altered. These data suggest that exposure to chronic social stress is associated with long-term selective reductions in serotonergic activity in the PFC. This effect may underlie the association in human beings between reduced serotonergic function and conditions such as pathological grief and posttraumatic stress disorder.

Clinical assessment versus research methods in the assessment of suicidal behavior

OBJECTIVE

This study examined how accurately routine inpatient clinical assessments documented a history of overt suicidal behavior in inpatients with a diagnosis of major depressive episode. Secondary questions involved the exploration of possible factors influencing the quality of routine clinical documentation of suicidal behavior, such as lethality of attempts, axis II comorbidity, and presence of recent suicidal behavior.

METHOD

Hospital records for 50 patients, known to have a history of suicidal behavior on the basis of research ratings, were reviewed to assess reporting of the number of lifetime suicide attempts, suicidal ideation and planning behavior, most medically lethal suicide attempt, and family history of suicidal behavior. These measures of suicidal behavior were compared with a comprehensive research assessment, completed concurrently and independently.

RESULTS

At admission clinicians failed to document a history of suicidal behavior in 12 of 50 patients identified by research assessment as depressed and as having attempted suicide. Fewer total suicide attempts were clinically reported than in research data. Documentation of suicidal behavior was least accurate in the physician discharge summary and was most accurate on hospital intake assessment, which employed a semistructured format for recording clinical information including suicidal behavior.

CONCLUSIONS

A significant degree of past suicidal behavior is not recorded during routine clinical assessment, and the use of semistructured screening instruments may improve documentation and detection of lifetime suicidal behavior. The physician discharge summary must accurately document suicidal behavior, since it best identified a high-risk population for out-patient clinicians responsible for follow-up.

Effect of chemical stimulation of the dorsal raphe nucleus on cerebral blood flow in rat

We have previously shown that electrical stimulation of the dorsal raphe nucleus (DRN) can increase or decrease cerebral blood flow (CBF). We now sought to determine whether the CBF responses are mediated by DRN neurons or fibers of passage. In anesthetized rat, the DRN was stimulated chemically (L-glutamate, kainate) and CBF in parietal cortex was measured by laser-Doppler flowmetry. Microinjection of kainate (5 nmol), but not L-glutamate, into DRN increased CBF (28 +/- 22%; P < 0.05). Decreased CBF to DRN stimulation was not observed. We conclude that stimulation of DRN neurons increases CBF.

Localized alterations in pre- and postsynaptic serotonin binding sites in the ventrolateral prefrontal cortex of suicide victims

Altered serotonin indices have been reported in the brain of suicide victims. We sought to localize the changes in presynaptic and postsynaptic serotonin receptors and identify an area of prefrontal cortex that may influence suicide risk. Quantitative autoradiography was performed in coronal sections of prefrontal cortex to determine whether serotonin 5-HT1A receptor (postsynaptic in cortex) and serotonin transporter (presynaptic) binding are different in suicide victims compared to matched controls. 5-HT1A receptor binding was higher in 85 of the 103 sampled areas in the suicide group (n = 18 pairs; P < 0.0001). The increase ranged from 17 to 30%. The increase was more pronounced in the ventrolateral prefrontal cortex. Serotonin transporter binding was found to be lower in the suicide group in all but one of the 43 sampled regions (n = 22 pairs; P < 0.0001). The reduction in binding was most pronounced in the ventrolateral prefrontal cortex, where the difference between suicides and controls ranged between 15 and 27%. Serotonin transporter and 5-HT1A binding were negatively correlated (r = -0.35 to -0.44, P = 0.04 to 0.007) within the same brain areas, suggesting common regulatory factors with opposite effects on binding to the two receptors. We conclude that suicide victims have an abnormality in the serotonin system involving predominantly the ventrolateral prefrontal cortex, and hypothesize that the serotonergic dysfunction in this brain region contributes to the risk for suicidal behavior.

Blunted serotonergic responsivity in depressed inpatients

We found a 38% lower maximal prolactin response to an oral challenge dose of 60 mg of dl-fenfluramine relative to placebo in younger (< 30 years) depressed inpatients compared with the response in age-matched healthy controls (p < .03). Severity of depression did not correlate with prolactin response. Prolactin responses in older depressed patients (> or = 30 years) did not differ from older controls. Younger depressed patients differed from older depressed patients in terms of earlier age of onset of first lifetime episode of major depression, greater degree of suicidal intent during a recent suicide attempt, double the level of hopelessness on admission to hospital, and a higher rate of comorbid borderline personality disorder. A blunted prolactin response to fenfluramine may be interpreted as evidence for reduced serotonergic function in younger depressed patients and may underlie their observed greater suicidality and hopelessness.

Major depression and the risk of attempted suicide

We examined the risk of attempted suicide in 100 inpatients during a major depressive episode. We hypothesized that patients who attempt suicide have a vulnerability for suicidal behavior independent of severity or duration of depression, manifested by suicide attempts early in the course of a depressive episode. The first 3 months after the onset of an MDE and the first 5 years after the lifetime onset of major depressive disorder represented the highest-risk period for attempted suicide, independent of the severity or duration of depression. Familial, genetic, early-life loss experiences and comorbid alcoholism may be causal factors.

Disproportionate suicidality in patients with comorbid major depression and alcoholism

OBJECTIVE

The two purposes of this study were to provide a comprehensive description of the clinical features of patients who presented to an intake psychiatric setting with major depression and alcohol dependence and to determine which clinical features distinguished this dual-diagnosis group from patients with the two relevant single diagnoses.

METHOD

During a recent 5-year period, a total of 107 patients who came to a psychiatric facility for initial evaluation were diagnosed as having both major depression and alcohol dependence. The clinical profile of this dual-diagnosis group was compared to that of nondepressed alcoholics (N = 497) and nonalcoholic patients with major depression (N = 5,625), assessed at the same facility, on the basis of information from the Initial Evaluation Form, a semistructured instrument containing a standardized symptom inventory that includes ratings of severity.

RESULTS

The psychiatric symptom that most strongly distinguished the depressed alcoholics from the two comparison groups was the level of suicidality. The depressed alcoholics differed significantly from the nonalcoholic depressed patients on only two depressive symptoms, suicidality (59% higher) and low self-esteem (22% higher); they were also significantly distinguished from the nonalcoholic depressed patients by factors such as greater impulsivity, functional impairment, and abnormal personal and social history markers.

CONCLUSIONS

Suicidality was disproportionately greater than other psychiatric symptoms in the depressed alcoholics. The clinical profile of depressed alcoholics suggests that they suffer an additive or synergistic effect of two separate disorders, resulting in a disproportionately high level of acute suicidality upon initial psychiatric evaluation.

Aggression and brain serotonergic responsivity: response to slides in male macaques

The association between central serotonergic responsivity (measured by prolactin response to acute administration of fenfluramine hydrochloride) and aggressivity was examined in 40 adult male cynomolgus monkeys (Macaca fascicularis). Prolactin response to fenfluramine was distributed bimodally with 24 monkeys displaying a "low" prolactin response and 15 showing a "high" prolactin response to the fenfluramine challenge. Behavioral responsivity was assessed by placing the monkeys individually in an open-field enclosure and presenting a series of photographic slides depicting both threatening and nonthreatening images. Monkeys that were low prolactin responders displayed significantly more aggressive gestures in response to a threatening slide of a human being than did the high responders (p < 0.05). Insofar as fenfluramine-stimulated prolactin release assesses serotonergic responsivity, these data support related findings in people and nonhuman primates linking reduced serotonergic activity and aggression.

Localization of corticotropin-releasing hormone in the human locus coeruleus and pedunculopontine tegmental nucleus: an immunocytochemical and in situ hybridization study

The present study utilized immunocytochemistry and in situ hybridization histochemistry to examine the localization of corticotropin-releasing hormone immunoreactivity and messenger RNA in neurons of the human brainstem. A large population of corticotropin-releasing hormone-immunoreactive neurons appeared in the lateral region of the pontomesencephalic tegmentum. These corticotropin-releasing hormone-containing neurons are predominantly located in the compact subnucleus of the pedunculopontine tegmental nucleus. Proceeding caudally, corticotropin-releasing hormone-immunoreactive neurons in the pedunculopontine tegmental nucleus travel in a dorsomedial direction approaching the ventral border of the locus coeruleus in a dispersed fashion and cluster in a region ventromedial to the locus coeruleus which corresponds to the ventral aspect of the laterodorsal tegmental nucleus. Dense corticotropin-releasing hormone-immunoreactive fibers are present in the dorsal portion of the locus coeruleus and are most prominent in the middle to rostral levels of the nucleus. The cellular and regional localization of corticotropin-releasing hormone messenger RNA in the human brainstem is identical to the perikaryal distribution visualized by immunocytochemistry. Neurons in the laterodorsal tegmental nucleus and pedunculopontine tegmental nucleus express abundant levels of corticotropin-releasing hormone messenger RNA as revealed by dense silver grains overlying these neurons on the emulsion autoradiograms. Within the locus coeruleus, the cellular expression of corticotropin-releasing hormone-immunoreactive and corticotropin-releasing hormone messenger RNA is exclusively localized to non-pigmented neurons. The present study confirms a previous finding describing dense corticotropin-releasing hormone-immunoreactive fibers innervating the human locus coeruleus and extends these findings by identifying corticotropin-releasing hormone immunoreactive and corticotropin-releasing hormone messenger RNA-containing perikarya in the pedunculopontine tegmental nucleus, in the ventral portion of the laterodorsal tegmental nucleus and in the locus coeruleus proper. From morphological observations, the corticotropin-releasing hormone-containing neurons in human pontomesencephalic tegmentum form a continuous population of neurons that are positioned anatomically to exert a putative neuromodulatory influence on locus coeruleus neurons.

Demonstration of an association among dietary cholesterol, central serotonergic activity, and social behavior in monkeys

Epidemiologic studies link plasma cholesterol reduction to increased mortality rates as a result of suicide, violence, and accidents. Deficient central serotonergic activity is similarly associated with violence and suicidal behavior. We investigated the relationship among dietary and plasma cholesterol, social behavior, and the serotonin system as a possible explanation for these findings. Juvenile cynomolgus monkeys (eight female and nine male) were fed a diet high in fat and either high or low in cholesterol. We then evaluated their behavior over an 8-month period. Plasma lipids and cerebrospinal fluid metabolites of serotonin, norepinephrine, and dopamine were assessed on two occasions, at 4 and 5.5 months after the initiation of behavioral observations. Animals that consumed a low-cholesterol diet were more aggressive, less affiliative, and had lower cerebrospinal fluid concentrations of 5-hydroxyindoleacetic acid than did their high-cholesterol counterparts (p < .05 for each). The association among dietary cholesterol, serotonergic activity, and social behavior was consistent with data from other species and experiments and suggested that dietary lipids can influence brain neurochemistry and behavior; this phenomenon could be relevant to our understanding of the increase in suicide and violence-related death observed in cholesterol-lowering trials.

Hopelessness in suicide attempters after acute treatment of major depression in late life

The relation between hopelessness and suicide attempts in the elderly was examined by studying the course of hopelessness in depressed patients. Sixty-three elderly patients with recurrent major depression were treated with nortriptyline and interpersonal psychotherapy and underwent serial ratings of hopelessness and depression during the acute and continuation phases of treatment. Patients who had made a suicide attempt in the past had significantly higher hopelessness scores than nonattempters during both phases of treatment. They were also more likely to drop out of treatment. A high degree of hopelessness persisting after remission of depression in elderly patients appears to be associated with a history of suicidal behavior. It may also increase the likelihood of premature discontinuation of treatment and lead to future suicide attempts or suicide.

Fewer pigmented neurons in the locus coeruleus of uncomplicated alcoholics

Altered noradrenergic function is associated with alcoholism. Reduced brain norepinephrine (NE) concentrations and beta-adrenergic receptor supersensitivity following chronic alcohol consumption suggest a reduced level of noradrenergic neurotransmission. To further elucidate the reason for changes in noradrenergic function, we determined the number of melanin-containing noradrenergic neurons in the locus coeruleus (LC) postmortem from 11 controls and 7 alcoholics. Controls did not have a known history of psychiatric or neurologic disorders and were drug-free by toxicological screen. The diagnosis of alcohol-dependence was based on DSM-III-R criteria. Alcoholics differed from controls in having 23% fewer LC neurons (control: 43,472 +/- 1,021; alcoholic: 33,398 +/- 2184; P < 0.0005) and 46% lower density of neurons (control: 1,227 +/- 89 cells per mm3; alcoholic: 663 +/- 94 cells per mm3; P = 0.001). The reduction in neurons was bilateral and throughout the middle third of the LC. The two groups did not differ with respect to LC length (control: 16.1 +/- 0.6 mm; alcoholic 15.3 +/- 0.9 mm; P = 0.47) or total LC volume (control: 37.3 +/- 2.8 mm3; alcoholic: 46.5 +/- 4.2 mm3; P = 0.09). Changes in noradrenergic neurotransmission in alcoholics may be due to fewer noradrenergic neurons in the locus coeruleus and may contribute to memory loss and depression, common consequences of alcoholism.

Expression of serotonin transporter messenger RNA in the human brain

The characterization and cellular localization of human brain mRNA encoding the serotonin transporter were investigated using northern blot analysis and in situ hybridization histochemistry. In contrast to results from rodent studies, in which single hybridizing mRNAs are detected in brain and periphery, northern analysis of human midbrain raphe tissue revealed the presence of three mRNA species absent from samples prepared from substantia nigra/ventral tegmental area. In situ hybridization studies revealed dense hybridization signal corresponding to serotonin transporter mRNA highly localized to neurons of the dorsal and median raphe nuclei and the caudal linear nucleus. No hybridization signal was observed in neurons of the substantia nigra or locus ceruleus. These findings demonstrate the first anatomical visualization of human brain serotonin transporter gene expression and reveal heterogeneity associated with serotonin transporter transcripts, similar to, but distinct from the pattern of expression visualized in human peripheral tissues.

The relationship of platelet 5-HT2 receptor indices to major depressive disorder, personality traits, and suicidal behavior

Previous research has suggested that major depression and suicidal behavior may be associated with altered serotonin receptor function. In this study, platelet serotonin2 (5-HT2) receptor binding indices were measured in conjunction with serotonin-amplified platelet aggregation, a response mediated by the platelet 5-HT2 receptor complex, in depressed patients and normal controls. The magnitude of serotonin-amplified platelet aggregation was positively correlated with the number of platelet 5-HT2 receptor sites in both groups. Mean values for the receptor binding indices and the receptor-mediated response did not differ significantly between patients and controls, although patients exhibited a wider range of values for each parameter compared with controls. Exploratory analyses were undertaken to determine clinical variables that might contribute to the increased variance in depressed individuals. These analyses failed to reveal a statistically significant relationship between any of the platelet 5-HT2 receptor measures and the subtype or severity of depressive illness, or the presence of comorbid borderline personality disorder. Although the mean number of receptor sites did not differ between patients who had recently attempted suicide and those who had never attempted suicide, a strong positive correlation (p = 0.002) was found between receptor number and the degree of medical damage resulting from the suicidal act. Furthermore, the ratio of the serotonin-amplified platelet aggregation response to platelet 5-HT2 receptor number, an index of the mean responsivity of an individual receptor complex, was lower in suicide attempters versus nonattempters (p = 0.06) and normal controls (p = 0.01). Exploratory analyses also suggested that recent exposure to psychotropic medication may result in a significant increase in platelet 5-HT2 receptor number (p = 0.03). Thus, although the study did not show a consistent alteration in platelet 5-HT2 receptor indices in major depression, the data suggest that specific factors such as suicidality and drug exposure may explain some of the variance in depressed patients.

Similar effects of glycine, zinc and an oxidizing agent on [3H]dizocilpine binding to the N-methyl-D-aspartate receptor in neocortical tissue from suicide victims and controls

This study used [3H]dizocilpine (MK-801) binding to the N-methyl-D-aspartate (NMDA) receptor to examine glycine, redox and zinc modulatory sites in membranes derived from the frontal and parietal cortex of control subjects (n = 8) and suicide victims (n = 6). [3H]dizocilpine binding in the presence of glutamate and glutamate plus glycine was similar in control and suicide subjects. The sulphydryl redox site was assessed using the oxidizing agent 5,5'-dithio-bis (2-nitrobenzoic acid), which inhibited binding in a dose-dependent fashion. Both redox and zinc sites were unaffected in the frontal and parietal cortex of suicide victims. These data indicate that the NMDA receptor and its glycine, redox and zinc subsites are preserved in the neocortex of suicide victims.

Abnormal behavioral responses to fenfluramine in patients with affective and personality disorders. Correlation with increased serotonergic responsivity

Serotonergic responsivity was assessed in 20 psychiatric patients by the prolactin response to a fenfluramine challenge test. During the fenfluramine challenge 6 of 20 patients (30%) spontaneously reported psychopathologic reactions that included: increased anxiety/agitation, psychotic symptoms, illusions, mood elevation, and anergia. The time of peak behavioral symptoms (2.5 +/- 0.8 hrs) corresponded closely to the time of peak increase in prolactin levels (3.0 +/- 1.1 hr). Abnormal behavioral responders had statistically significant greater increases in prolactin 1 to 4 hr after fenfluramine when compared to normal responders. Patients who developed an abnormal psychopathologic response to fenfluramine were characterized by higher levels of anxiety and agitation at the time of admission to the hospital but otherwise were not distinguishable on the basis of severity of other psychiatric symptoms. This study suggests that increased serotonergic transmission may trigger anxiety, psychosis, and mood elevation in specific vulnerable individuals, whereas other patients with similar psychiatric illnesses are not affected.

Elucidation of biochemical basis of the antidepressant action of electroconvulsive therapy by human studies

A variety of direct and indirect human studies indicate that electroconvulsive therapy (ECT) enhances transmission in a number of key transmitter systems in the brain. These include the noradrenergic system, the serotonergic system, and the GABAergic and dopaminergic systems. On the other hand, ECT probably reduces cholinergic transmission. The enhanced transmission effects have been related to the antidepressant effect of ECT, whereas the cholinergic effect has been attributed to its effects on memory and cognition as well as depression. This paper will briefly review the research methodologies and results from clinical studies of neurotransmitter effects of ECT. Promising future directions of research will be indicated.

Neuroendocrine responses to fenfluramine challenge are influenced by exposure to chronic social stress in adult male cynomolgus macaques

This study was designed to investigate the effect of chronic social stress on central serotonergic responsivity in adult male cynomolgus monkeys (Macaca fascicularis). The influences of social stress and dominance status (social rank) on adrenocorticotropin hormone (ACTH) and cortisol responses to acute administration of an indirect serotonergic agonist (fenfluramine) were evaluated in 75 cynomolgus macaques that were housed in five-member social groups for 28 mo. These groups either remained stable in composition (No-Stress) or had their composition periodically reorganized in the first (Early-Stress) or second (Late-Stress) halves of the study. At the end of the 23rd month, a fenfluramine challenge was done. Animals in the Late-Stress condition had significantly higher ACTH responses compared to those in the No-Stress condition (p < .05) and significantly higher cortisol responses compared to those in the Early-Stress condition (p < .05). No differences between dominant and subordinate animals in ACTH or cortisol responses to challenge were identified. These data suggest that social stress produces a "state"-related augmentation of hypothalamic-pituitary-adrenal responsivity to fenfluramine (serotonergic) challenge in cynomolgus macaques.