Pindolol pretreatment blocks stimulation by meta-chlorophenylpiperazine of prolactin but not cortisol secretion in normal men

The 5-HT2C receptor agonist meta-chlorophenylpiperazine (mCPP) reduces palatable food consumption and BOLD fMRI responses to food images in healthy female volunteers

RATIONALE

Brain 5-HT_2C receptors form part of a neural network that controls eating behaviour. 5-HT_2C receptor agonists decrease food intake by activating proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus, but recent research in rodents has suggested that 5-HT_2C receptor agonists may also act via dopaminergic circuitry to reduce the rewarding value of food and other reinforcers. No mechanistic studies on the effects of 5-HT_2C agonists on food intake in humans have been conducted to date.

OBJECTIVES

The present study examined the effects of the 5-HT_2C receptor agonist meta-chlorophenylpiperazine (mCPP) on food consumption, eating microstructure and blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) responses to food pictures in healthy female volunteers.

METHODS

In a double-blind, placebo-controlled, crossover design, participants were randomized immediately after screening to receive oral mCPP (30mg) in a single morning dose, or placebo, in a counterbalanced order. Test foods were served from a Universal Eating Monitor (UEM) that measured eating rate and fMRI BOLD signals to the sight of food and non-food images were recorded.

RESULTS

mCPP decreased rated appetite and intake of a palatable snack eaten in the absence of hunger but had no significant effect on the consumption of a pasta lunch (although pasta eating rate was reduced). mCPP also decreased BOLD fMRI responses to the sight of food pictures in areas of reward-associated circuitry. A post hoc analysis identified individual variability in the response to mCPP (exploratory responder-non-responder analysis). Some participants did not reduce their cookie intake after treatment with mCPP and this lack of response was associated with enhanced ratings of cookie pleasantness and enhanced baseline BOLD responses to food images in key reward and appetite circuitry.

CONCLUSIONS

These results suggest that 5-HT_2C receptor activation in humans inhibits food reward-related responding and that further investigation of stratification of responding to mCPP and other 5-HT_2C receptor agonists is warranted.

Serotonergic 5-HT2A/2C receptors are involved in prolactin secretion in hyperestrogenic rats

Serotonin (5-HT) has been shown to participate in prolactin secretion through a complex process resulting in both positive and negative effects. Estrogen has also been recognized as being involved in this serotonergic effect on prolactin release. Therefore, the aim of the present study was to assess whether estradiol modulates serotonergic involvement in prolactin secretion though 5-HT1A and/or 5-HT2A/2C receptors. Ovariectomized female Wistar rats, treated for 2 weeks with estrogen to induce a hyperprolactinemic status (hyperestrogenic rats) or with sunflower oil vehicle (hypoestrogenic rats), were injected daily with normal saline solution or 6-chloro-2-(1-piperazinyl)pyrazine (MK-212), an 5-HT2A/2C receptor agonist, for 4 days. Other groups of ovariectomized animals received 8-hydroxy-2-(di-N-propylamino)tetralin (8-OH-DPAT) or pindolol, an agonist and antagonist of the 5-HT1A receptor respectively, on the last day of treatment with estrogen or vehicle. Prolactin levels were compared among groups in each experiment under the distinct drug treatments. MK-212 was found to increase prolactin concentrations both in hyper- and hypoestrogenic females compared to controls (p<0.05). In contrast, prolactin levels remained similar to those of controls both in hyperestrogenic animals treated with 8-OH-DPAT and pindolol and in hypoestrogenic rats administered the same treatments. In conclusion, our findings indicate the involvement of 5-HT2A/2C receptors on prolactin release through serotonergic pathways in female animals, especially in hyperestrogenic states.

The neuropharmacology of prolactin secretion elicited by 3,4-methylenedioxymethamphetamine ("ecstasy"): a concurrent microdialysis and plasma analysis study

3,4-methylenedioxymethamphetamine (MDMA) is a substituted phenethylamine that is widely abused as the street drug "ecstasy". Racemic MDMA (S,R(+/-)-MDMA) and its stereoisomers elicit complex spectrums of psychobiological, neurochemical, and hormonal effects. In this regard, recent findings demonstrated that S,R(+/-)-MDMA and its stereoisomer R(-)-MDMA elicit increases in striatal extracellular serotonin levels and plasma levels of the hormone prolactin in rhesus monkeys. In the present mechanistic study, we evaluated the role of the serotonin transporter and the 5-HT(2A) receptor in S,R(+/-)-MDMA- and R(-)-MDMA-elicited prolactin secretion in rhesus monkeys through concurrent microdialysis and plasma analysis determinations and drug interaction experiments. Concurrent neurochemical and hormone determinations showed a strong positive temporal correlation between serotonin release and prolactin secretion. Consistent with their distinct mechanisms of action and previous studies showing that the serotonin transporter inhibitor fluoxetine attenuates the behavioral and neurochemical effects of S,R(+/-)-MDMA, pretreatment with fluoxetine attenuated serotonin release elicited by either S,R(+/-)-MDMA or R(-)-MDMA. As hypothesized, at a dose that had no significant effects on circulating prolactin levels when administered alone, fluoxetine also attenuated prolactin secretion elicited by S,R(+/-)-MDMA. In contrast, combined pretreatment with both fluoxetine and the selective 5-HT(2A) receptor antagonist M100907 was required to attenuate prolactin secretion elicited by R(-)-MDMA, suggesting that this stereoisomer of S,R(+/-)-MDMA elicits prolactin secretion through both serotonin release and direct agonism of 5-HT(2A) receptors. Accordingly, these findings inform our understanding of the neuropharmacology of both S,R(+/-)-MDMA and R(-)-MDMA and the regulation of prolactin secretion.

Contributions of serotonin in addiction vulnerability

The serotonin (5-hydroxytryptamine; 5-HT) system has long been associated with mood and its dysregulation implicated in the pathophysiology of mood and anxiety disorders. While modulation of 5-HT neurotransmission by drugs of abuse is also recognized, its role in drug addiction and vulnerability to drug relapse is a more recent focus of investigation. First, we review preclinical data supporting the serotonergic raphe nuclei and their forebrain projections as targets of drugs of abuse, with emphasis on the effects of psychostimulants, opioids and ethanol. Next, we examine the role of 5-HT receptors in impulsivity, a core behavior that contributes to the vulnerability to addiction and relapse. Finally, we discuss evidence for serotonergic dysregulation in comorbid mood and addictive disorders and suggest novel serotonergic targets for the treatment of addiction and the prevention of drug relapse.

Endocrine and neurochemical effects of 3,4-methylenedioxymethamphetamine and its stereoisomers in rhesus monkeys

3,4-Methylenedioxymethamphetamine (MDMA) is an amphetamine derivative that elicits complex biological effects in humans. One plausible mechanism for this phenomenon is that racemic MDMA is composed of two stereoisomers that exhibit qualitatively different pharmacological effects. In support of this, studies have shown that R(-)-MDMA tends to have hallucinogen-like effects, whereas S(+)-MDMA tends to have psychomotor stimulant-like effects. However, relatively little is known about whether these stereoisomers engender different endocrine and neurochemical effects. In the present study, the endocrine and neurochemical effects of each stereoisomer and the racemate were assessed in four rhesus monkeys after intravenous delivery at doses (1-3 mg/kg) that approximated voluntary self-administration by rhesus monkeys and human recreational users. Specifically, fluorescence-based enzyme-linked immunosorbent assay was used to assess plasma prolactin concentrations, and in vivo microdialysis was used to assess extracellular dopamine and serotonin concentrations in the dorsal striatum. R(-)-MDMA, but not S(+)-MDMA, significantly increased plasma prolactin levels and the effects of S,R(+/-)-MDMA were intermediate to each of its component stereoisomers. Although S(+)-MDMA did not alter prolactin levels, it did significantly increase extracellular serotonin concentrations. In addition, S(+)-MDMA, but not R(-)-MDMA, significantly increased dopamine concentrations. Furthermore, as in the prolactin experiment, the effects of the racemate were intermediate to each of the stereoisomers. These studies demonstrate the stereoisomers of MDMA engender qualitatively different endocrine and neurochemical effects, strengthening the inference that differences in these stereoisomers might be the mechanism producing the complex biological effects of the racemic mixture of MDMA in humans.

Serotonin dysfunction in pathological gamblers: increased prolactin response to oral m-CPP versus placebo

OBJECTIVE

Acute administration of the partial serotonin (5-HT) agonist meta-chlorophenylpiperazine (m-CPP), that is used also as a street drug, has been reported to induce a "high" and craving response in various impulsive and substance addiction disorders.

INTRODUCTION

To clarify altered 5-HT metabolism in pathological gamblers and to explore the specific role of serotonergic system in non-substance addictions, we assessed behavioral ("high" and "craving") and neuroendocrine (prolactin and cortisol) responses to an oral single dose of m-CPP and placebo in pathological gamblers and matched controls. Moreover, the relationship between neuroendocrine outcome and clinical severity has been assessed.

METHOD

Twenty-six pathological gamblers and 26 healthy control subjects enter a double-blind, placebo-controlled-crossed administration of orally dose m-CPP 0.5 mg/kg. Outcome measures included prolactin and cortisol levels, gambling severity, mood, craving and "high" scales.

RESULTS

Pathological gamblers had significantly increased prolactin response compared to controls at 180 minutes and at 210 minutes post-administration. Greater pathological gamblers severity correlated with increased neuroendocrine responsiveness to m-CCP, suggesting greater 5-HT dysregulation. Pathological gambling patients had a significantly increased "high" sensation after m-CPP administration compared with control.

CONCLUSION

These results provide additional evidence for 5-HT disturbance in pathological gamblers and they support the hypotheses that the role of the 5-HT dysfunction related to the experience of "high" might represent the pathway that leads to dyscontrolled behavior in pathological gamblers. Furthermore, the "high" feeling induced by m-CPP in pathological subjects may represent a marker of vulnerability to both behavioral and substance addictions.

gamma-Aminobutyric acid-serotonin interactions in healthy men: implications for network models of psychosis and dissociation

BACKGROUND

This study tested the hypothesis that deficits in gamma-aminobutyric acid type A (GABA(A)) receptor function might create a vulnerability to the psychotogenic and perceptual altering effects of serotonergic (5-HT(2A/2C)) receptor stimulation. The interactive effects of iomazenil, an antagonist and partial inverse agonist of the benzodiazepine site of the GABA(A) receptor complex, and m-chlorophenylpiperazine (m-CPP), a partial agonist of 5-HT(2A/2C) receptors, were studied in 23 healthy male subjects.

METHODS

Subjects underwent 4 days of testing, during which they received intravenous infusions of iomazenil/placebo followed by m-CPP/placebo in a double-blind, randomized crossover design. Behavioral, cognitive, and hormonal data were collected before drug infusions and periodically for 200 min after.

RESULTS

Iomazenil and m-CPP interacted in a synergistic manner to produce mild psychotic symptoms and perceptual disturbances without impairing cognition. Iomazenil and m-CPP increased anxiety in an additive fashion. Iomazenil and m-CPP interacted in a synergistic manner to increase serum cortisol.

CONCLUSIONS

Gamma-aminobutyric acid-ergic deficits might increase the vulnerability to the psychotomimetic and perceptual altering effects of serotonergic agents. These data suggest that interactions between GABA(A) and 5-HT systems might contribute to the pathophysiology of psychosis and dissociative-like perceptual states.

Phase-shifts of 24-h rhythms of hormonal release and body temperature following early evening administration of the melatonin agonist agomelatine in healthy older men

OBJECTIVE

Older adults are less responsive to the phase-shifting effects of light than younger subjects and may have difficulties adapting to abrupt time shifts. This study aims to determine whether the potent melatonin agonist agomelatine (S-20098) is capable of phase-shifting overt circadian rhythms in older adults.

SUBJECTS AND DESIGN

Eight healthy elderly men participated in a double-blind, two-period, cross-over study of 15 days of daily administration of either agomelatine (50 mg) or placebo at 1830 h.

MEASUREMENTS

At the end of each treatment period, the 24-h profiles of body temperature and of the plasma levels of GH, PRL, cortisol and TSH were collected and sleep was monitored polygraphically.

RESULTS

Phase-advances, averaging nearly 2 h, were observed for the temperature profile and for the variables characterizing the temporal organization of cortisol secretion following agomelatine administration. A similar trend was observed for the circadian rise of plasma TSH. There was no effect of agomelatine on any of the sleep variables. Agomelatine stimulated GH secretion during the wake period and was associated with a transient elevation of PRL levels.

CONCLUSIONS

Melatonin agonists such as agomelatine may be useful to phase-shift at least some overt circadian rhythms in older adults.

The effect of mirtazapine augmentation of clozapine in the treatment of negative symptoms of schizophrenia: a double-blind, placebo-controlled study

The development of therapeutic strategies to effectively treat negative symptoms remains one of the primary goals in the treatment of schizophrenia. Mirtazapine is the first of a new class of dual action compounds, the noradrenergic and specific serotonergic antidepressants (NaSSa), whose activity is related to the enhancement of noradrenergic and serotonergic transmission by a presynaptic alpha2 antagonism and postsynaptic 5-HT2 and 5-HT3 antagonism, respectively. This study was a 8-week double-blind, randomized, placebo-controlled trial of 30 mg adjunctive mirtazapine to clozapine therapy in 24 patients with DSM-IV schizophrenia. The main finding at the end of the trial was a significant reduction on the Scale for the Assessment of Negative Symptoms (SANS) total scores in the mirtazapine group compared to placebo (P<0.01) with a significant improvement on the SANS subscales avolition/apathy and anhedonia/asociality. The Brief Psychiatric Rating Scale total score at week 8 showed superiority of mirtazapine over placebo. These findings suggest a potential role for mirtazapine as an augmentation strategy in the treatment of negative symptoms of schizophrenia.

Hormonal and temperature responses to flesinoxan in normal volunteers: an antagonist study

RATIONALE

Flesinoxan is a highly potent and selective 5-HT1A agonist. In a recent study, in normal volunteers, flesinoxan induced a significant and dose-dependent increase in adrenocorticotropic hormone (ACTH), cortisol, prolactin (PRL), growth hormone (GH) and a decrease in body temperature.

OBJECTIVES

In order to better define the role of 5-HT receptor subtypes in response to flesinoxan, we assessed the influence of 5-HT1A and 5-HT2 antagonists on hormonal and temperature responses to flesinoxan.

METHODS

Hormonal and temperature responses were studied in 6 volunteers with or without pretreatment with pindolol (30 mg p.o.), a 5-HT1A antagonist, or ritanserin (10 mg p.o.), a selective 5-HT2 antagonist, using a double-blind crossover design.

RESULTS

Pindolol significantly antagonized ACTH, PRL, GH and temperature responses to flesinoxan and ritanserin exhibited similar activity on PRL and ACTH responses.

CONCLUSIONS

These results show the role of 5-HT1A mechanisms in the PRL, ACTH, GH, and temperature responses to flesinoxan, and the role of 5-HT2 mechanisms in PRL and ACTH responses. Therefore, they confirm the interest of flesinoxan as a 5-HT neuroendocrine probe.

Cholesterol in mood and anxiety disorders: review of the literature and new hypotheses

Cholesterol plays an integral role in the structure and function of the cell membrane and may also affect neurotransmission in the central nervous system. Previous work has identified abnormalities in serum cholesterol levels in patients with mood and anxiety disorders as well as in suicidal patients. However, the biological significance of these abnormalities remains to be clarified. An understanding of how serum cholesterol relates to the pathophysiology of mood disorders may generate biological markers that predict treatment response as well as targets for novel therapeutic strategies. In this article, we review the literature studying the significance of cholesterol in mood and anxiety disorders, with an emphasis on new studies focusing on the adverse impact of hypercholesterolemia on the treatment of major depressive disorder (MDD). We then propose possible mechanisms that would account for the relationship between elevated cholesterol and treatment non-response in MDD.

Neurobiological correlates of diagnosis and underlying traits in patients with borderline personality disorder compared with normal controls

The purpose of the study was to test the hypothesis that borderline personality disorder (BPD) and its underlying traits are associated with abnormalities in neurotransmitter systems. Subjects were 30 women with BPD and 22 normal controls, assessed using the Diagnostic Interview for Borderlines, revised, the Hamilton Depression Scale (HAM-A) and the Hamilton Anxiety Scale (HAM-A), the Diagnostic Assessment of Personality Pathology, the Buss-Durkee Guilt-Hostility Inventory, the Barratt Impulsivity Scale (BIS), and challenge tests to measure serotonergic, cholinergic and noradrenergic activity. Borderline subjects with high HAM-A and HAM-D scores showed a faster time to peak in prolactin response to meta-chlorphenylpiperazine (m-CPP) challenge. Borderline subjects with high BIS scores showed prolactin blunting. There were no differences in cortisol response to m-CPP, or on the cholinergic and noradrenergic challenges. The results suggest that impulsive traits in borderline patients are associated with abnormalities in serotonergic systems.

The pharmacology and clinical pharmacology of 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy")

The amphetamine derivative (+/-)-3,4-methylenedioxymethamphetamine (MDMA, ecstasy) is a popular recreational drug among young people, particularly those involved in the dance culture. MDMA produces an acute, rapid enhancement in the release of both serotonin (5-HT) and dopamine from nerve endings in the brains of experimental animals. It produces increased locomotor activity and the serotonin behavioral syndrome in rats. Crucially, it produces dose-dependent hyperthermia that is potentially fatal in rodents, primates, and humans. Some recovery of 5-HT stores can be seen within 24 h of MDMA administration. However, cerebral 5-HT concentrations then decline due to specific neurotoxic damage to 5-HT nerve endings in the forebrain. This neurodegeneration, which has been demonstrated both biochemically and histologically, lasts for months in rats and years in primates. In general, other neurotransmitters appear unaffected. In contrast, MDMA produces a selective long-term loss of dopamine nerve endings in mice. Studies on the mechanisms involved in the neurotoxicity in both rats and mice implicate the formation of tissue-damaging free radicals. Increased free radical formation may result from the further breakdown of MDMA metabolic products. Evidence for the occurrence of MDMA-induced neurotoxic damage in human users remains equivocal, although some biochemical and functional data suggest that damage may occur in the brains of heavy users. There is also some evidence for long-term physiological and psychological changes occurring in human recreational users. However, such evidence is complicated by the lack of knowledge of doses ingested and the fact that many subjects studied are or have been poly-drug users.

Serotonin and the neuroendocrine regulation of the hypothalamic--pituitary-adrenal axis in health and disease

Serotonin (5-hydroxytryptamine, 5-HT)-containing neurons in the midbrain directly innervate corticotropin-releasing hormone (CRH)-containing cells located in paraventricular nucleus of the hypothalamus. Serotonergic inputs into the paraventricular nucleus mediate the release of CRH, leading to the release of adrenocorticotropin, which triggers glucocorticoid secretion from the adrenal cortex. 5-HT1A and 5-HT2A receptors are the main receptors mediating the serotonergic stimulation of the hypothalamic-pituitary-adrenal axis. In turn, both CRH and glucocorticoids have multiple and complex effects on the serotonergic neurons. Therefore, these two systems are interwoven and communicate closely. The intimate relationship between serotonin and the hypothalamic-pituitary-adrenal axis is of great importance in normal physiology such as circadian rhythm and stress, as well as pathophysiological disorders such as depression, anxiety, eating disorders, and chronic fatigue.

D-fenfluramine-evoked serotonergic responses in olanzapine-treated schizophrenic patients

Antagonist activity at the 5-HT(2) receptor may contribute to the therapeutic efficacy of atypical antipsychotics in schizophrenia. This neuroendocrine study examined the in vivo functional serotonergic (5-HT) activity of the atypical antipsychotic olanzapine. We examined central 5-HT(2) responses by measuring the serum prolactin (PRL) over 5 h in response to 30 mg of D-fenfluramine (DFEN) in two groups of male schizophrenic patients. Blunted PRL responses to DFEN indicate functional 5-HT(2) receptor antagonism. Seven patients treated with olanzapine at a mean (S.D.) dose of 13.1 (4.6) for a mean of 28 weeks were compared with a matched group of eight patients who had received no antipsychotic treatment for at least 2 weeks. Baseline PRL levels did not differ significantly in the two patient groups and were within the normal range. The olanzapine-treated patients showed a significantly lower maximal DFEN-evoked PRL response and a significantly lower group x time overall PRL release compared with the untreated patient group. We have previously demonstrated a similar degree of functional in vivo 5-HT(2) antagonism with the atypical antipsychotic clozapine. This study thus suggests that this activity may not contribute to the unique clinical efficacy of clozapine.

Thyroid hormones, serotonin and mood: of synergy and significance in the adult brain

The use of thyroid hormones as an effective adjunct treatment for affective disorders has been studied over the past three decades and has been confirmed repeatedly. Interaction of the thyroid and monoamine neurotransmitter systems has been suggested as a potential underlying mechanism of action. While catecholamine and thyroid interrelationships have been reviewed in detail, the serotonin system has been relatively neglected. Thus, the goal of this article is to review the literature on the relationships between thyroid hormones and the brain serotonin (5-HT) system, limited to studies in adult humans and adult animals. In humans, neuroendocrine challenge studies in hypothyroid patients have shown a reduced 5-HT responsiveness that is reversible with thyroid replacement therapy. In adult animals with experimentally-induced hypothyroid states, increased 5-HT turnover in the brainstem is consistently reported while decreased cortical 5-HT concentrations and 5-HT2A receptor density are less frequently observed. In the majority of studies, the effects of thyroid hormone administration in animals with experimentally-induced hypothyroid states include an increase in cortical 5-HT concentrations and a desensitization of autoinhibitory 5-HT1A receptors in the raphe area, resulting in disinhibition of cortical and hippocampal 5-HT release. Furthermore, there is some indication that thyroid hormones may increase cortical 5-HT2 receptor sensitivity. In conclusion, there is robust evidence, particularly from animal studies, that the thyroid economy has a modulating impact on the brain serotonin system. Thus it is postulated that one mechanism, among others, through which exogenous thyroid hormones may exert their modulatory effects in affective illness is via an increase in serotonergic neurotransmission, specifically by reducing the sensitivity of 5-HT1A autoreceptors in the raphe area, and by increasing 5-HT2 receptor sensitivity.

Psychomotor slowing, neuroendocrine responses, and behavioral changes after oral administration of meta-chlorophenylpiperazine in normal volunteers

The mixed 5-HT receptor agonist/antagonist meta-chlorophenylpiperazine (mCPP) is known to suppress locomotor activity in mice and rats. This study aimed: (1) to determine whether mCPP induces cognitive and motor changes in normal human volunteers and how these changes relate to the neuroendocrine effects of mCPP; and (2) to compare these cognitive and motor changes to the known cognitive and motor slowing patterns in depression and schizophrenia. A computerized method (used in previous research) analyzed fine motor behavior during figure-copying tasks. In 14 normal male volunteers behavioral responses, body temperature, plasma levels of prolactin and cortisol, and cognitive and motor performance during figure-copying tasks were measured after a single oral dose of mCPP (0.5 mg/kg). mCPP-induced prolongation of the reaction times in all copying tasks, parallel to increases in cortisol and prolactin and some self-reported behavioral effects. There were no changes in the movement times or the velocities of the writing movements. In conclusion, mCPP induced cognitive, but not motor slowing, in normal male volunteers. This indicates that the human serotonin system is also implicated in psychomotor behavior. This pattern of slowing was different from that in depressed and schizophrenic patients.

The effect of olanzapine treatment on m-chlorophenylpiperazine-induced hormone release in schizophrenia

In addition to dopamine, serotonin (5-hydroxytryptamine, 5-HT) has been reported to play an important role in schizophrenia. Besides blocking dopamine, atypical antipsychotics also block 5-HT receptors. The clinical efficacy of the atypical antipsychotic clozapine is associated with the 5-HT antagonistic action of the drug and a high serotonergic tone before treatment. The atypical antipsychotic olanzapine has a receptor-binding profile similar to that of clozapine. The present study investigated whether treatment with olanzapine blocks hormone release induced by the 5-HT2c agonist m-chlorophenylpiperazine (m-CPP) and, if so, whether this 5-HT antagonistic effect is related to treatment response. Eighteen male schizophrenic patients participated in this study. All patients were challenged with m-CPP (0.5 mg/kg orally) in a double-blind, randomized, placebo-controlled design after a drug-free period of at least 2 weeks. Adrenocorticotropic hormone (ACTH), cortisol, and prolactin plasma levels were measured every 30 minutes up to 210 minutes after challenge. Patients were treated for 6 weeks with 10 mg olanzapine daily in an open design, after which the challenge tests were repeated. Olanzapine significantly blocked m-CPP-induced ACTH, cortisol, and prolactin release, suggesting that it is a potent 5-HT2c antagonist in vivo. This 5-HT antagonistic effect of olanzapine was not significantly correlated with treatment response. Also, no significant correlation was found between m-CPP-induced hormone release before treatment and clinical response after treatment with olanzapine. These findings suggest that olanzapine is a potent 5-HT2c antagonist in vivo but that this is unrelated to its clinical efficacy in this nonrefractory sample of schizophrenic patients.

Pedophilia is accompanied by increased plasma concentrations of catecholamines, in particular epinephrine

Plasma epinephrine and norepinephrine concentrations were measured in pedophiles and normal men both in placebo conditions and after administration of meta-chlorophenylpiperazine (mCPP), a post-synaptic 5-HT2 receptor agonist. The plasma concentrations of catecholamines, in particular epinephrine, were significantly increased in pedophiles. It is concluded that pedophiles may have an increased activity of the sympathoadrenal system.

Serotonin transporter promoter polymorphism is associated with attenuated prolactin response to fenfluramine

Disturbances in central serotonin (5-HT) function may have a role in impulsive aggression in patients with a wide range of psychiatric diagnoses. The underlying mechanism, however, remains unknown. There are several naturally occurring mutations in the 5-HT signaling pathway that may underlie differences in 5-HT function and responsivity to drugs that affect 5-HT functioning. In the present study, we examined the relationship between polymorphisms in the promoter region of the gene coding for the neuronal 5-HT transporter, fenfluramine-induced prolactin release, and aggressive impulsivity (as measured by Barratt Impulsivity Scale, Buss-Durkee Hostility Inventory, and Brown-Goodwin Aggression Scale scores), in a group of abstinent alcoholic patients and healthy volunteers. We report here that possession of the short variant of the 5-HT transporter promoter polymorphism was associated with a blunting of overall central 5-HT function, as measured by fenfluramine-induced prolactin release. We found no relationship between aggressive, hostile, or impulsive traits and fenfluramine-induced prolactin release or between these traits and polymorphisms in the 5-HT transporter promoter. Thus, we have shown that a 5-HT transporter promoter genotype, which has previously been associated with anxiety-based behaviors, alters an in vivo measure of central 5-HT function (fenfluramine-induced prolactin release), providing an important mechanism for linkage between a gene, physiological function, and behavior. Published 2001 Wiley-Liss, Inc.

Neuroendocrine correlates of depression in abstinent heroin-dependent subjects

The functions of the central alpha-adrenergic, serotoninergic and dopaminergic systems were investigated in 28 heroin-dependent subjects 6-8 weeks after detoxification, and in 22 healthy control subjects (group C). Fourteen heroin-dependent subjects with depressive comorbidity (group A), and 14 heroin-dependent subjects without other Axis I and II pathologies (group B) were included among abstinent substance abusers. Norepinephrine (NE) function was evaluated by growth hormone (GH) responses to acute stimulation with clonidine (clon); serotonin (5-HT) function by prolactin (PRL) and cortisol (CORT) responses to acute stimulation with D-fenfluramine (D-fen) and dopamine (DA) function by GH and PRL responses to acute administration of bromocriptine (brom). Central NE activity, as measured by the GH-clon test, seems to be well preserved both in A and B subjects. PRL and CORT responses to D-fen were significantly blunted both in A subjects and in B subjects, in comparison with control subjects (C); the PRL response in A subjects was significantly lower than in B subjects. The DA system of B subjects was found unimpaired; in contrast, a significantly higher GH response to brom in A subjects (depressed) could express D2 post-synaptic receptor hypersensitivity and, therefore, decreased pre-synaptic DA release. In sum, the study of central monoamine function revealed an alteration only of the 5-HT system in detoxified heroin-dependent subjects without psychiatric comorbidity, which might be a trait character of these subjects, possibly involved in the pathogenesis of the disorder. A more significant impairment of 5-HT function and the hypersensitivity of post-synaptic DA receptors in A subjects suggests that specific biological correlates of psychiatric comorbidity may characterize substance abuser subtypes.

Provocation of neurocardiogenic syncope by clomipramine administration during the head-up tilt test in vasovagal syndrome

OBJECTIVES

We sought to test the hypothesis that activation of the serotonergic system in patients with vasovagal syndrome during the head-up tilt test provokes syncope.

BACKGROUND

Central serotonergic activation participates in the pathogenesis of neurocardiogenic syncope. Drugs increasing serotonin (5-HT) in the central nervous system have not been tested as drug challenges during the head-up tilt test with clomipramine (Clom-HUT).

METHODS

The serotonergic re-uptake inhibitor clomipramine was infused (5 mg in 5 min) at the start of Clom-HUT in 55 patients (mean age 40 +/- 17 years) with a positive history of recurrent neurocardiogenic syncope and in 22 healthy control subjects (mean age 46 +/- 15 years). Blood samples were taken at 0, 5, 10 and 20 min for estimation of plasma prolactin and cortisol as neuroendocrine indicators of central serotonergic responsivity. All subjects had been previously tested with a basic 60 degrees head-up tilt test (B-HUT) for 30 min, and if negative, isoproterenol infusion was given at the end of the test.

RESULTS

Twenty-nine (53%) of the 55 patients and none of the 22 control subjects had a positive result in the B-HUT. With Clom-HUT, the proportion of patients who experienced a positive response increased to 80% (n = 44), although this happened to only one control subject. Prolactin and cortisol plasma levels increased significantly in the positive Clom-HUT patient group only.

CONCLUSIONS

The results indicate an increased responsivity of the central serotonergic neural system in subjects with vasovagal syndrome, the activation of which leads to sympathetic withdrawal. The use of clomipramine infusion with the tilt test seems to considerably improve its diagnostic value.

Neuroendocrine correlates of temperamental traits in humans

Studies investigating temperament traits in humans and their biological correlates have found high levels of novelty seeking (NS) linked with dopaminergic system changes, and particularly a deficit of dopamine transporter. Harm avoidance and reward dependence, on the other hand, appeared to be associated, respectively with serotonin and noradrenaline changes. In the present study, we have investigated the dopaminergic (DA), serotonergic (5-HT), and noradrenergic (NE) functions in healthy volunteers by challenging the monoamine systems with the DA agonist bromocriptine, the 5-HT agonist D-fenfluramine, and the NE agonist clonidine, respectively. Parallel to this investigation, we examined the temperament traits of our subjects by measuring NS, harm avoidance (HA) and reward dependence (RD) using the 'Three-dimensional Personality Questionnaire' (TPQ). The aims of the study were to see whether or not the monoamine functions were correlated with temperament traits. Bromocriptine challenge induced a significant GH increase and a significant suppression of PRL. D-fenfluramine test significantly increased PRL and cortisol plasma levels and Clonidine test induced a significant rise in GH values. NS scores showed a significant direct correlation with brom-stimulated GH values (r=0.426, P<0.05) and a significant inverse correlation with brom-inhibited PRL values (r=-0.498, P<0.01). HA scores correlated significantly with D-fen-stimulated PRL and CORT AUCs, (PRL: r=0.424, P<0.05; CORT: r=0. 595, P<0.005). RD scores correlated positively with clon-stimulated GH values (r=0.55; F=8.6; P<0.01) and negatively with brom-inhibited-PRL AUCs (r=-0.439, P<0.05). Our data support Cloninger theory concerning the biological correlates of temperamental traits, and evidence the link between the neuroendocrine responses to dynamic challenges and stable temperament features.

Serotonergic blunting to meta-chlorophenylpiperazine (m-CPP) highly correlates with sustained childhood abuse in impulsive and autoaggressive female borderline patients

BACKGROUND

Disturbances of affect, impulse regulation, and autoaggressive behavior, which are all said to be related to an altered function of the central serotonergic (5-HT) system, are prominent features of borderline personality disorder (BPD). A high coincidence of childhood physical and sexual abuse is reported in these patients. Animal studies indicate that early, sustained stress correlates with a dysfunctional central 5-HT system. Therefore, we hypothesize that sustained traumatic stress in childhood affects the responsivity of the postsynaptic serotonergic system of traumatized BPD patients.

METHODS

Following Axis I, Axis II, and trauma assessment, a neuroendocrine challenge test was performed with the postsynaptic serotonergic agonist meta-chlorophenylpiperazine (m-CPP) in 12 impulsive and autoaggressive female patients with BPD and 9 matched healthy volunteers.

RESULTS

The cortisol and prolactin responses to the m-CPP challenge in BPD patients were significantly lower compared to those in controls. Within the group of patients with BPD, the net prolactin response showed a high inverse correlation with the frequency of the physical (r = -.77) and sexual abuse (r = -.60).

CONCLUSIONS

Our data suggest that severe and sustained traumatic stress in childhood affects the 5-HT system and especially 5-HT(1A) receptors. This finding confirms the data from animal research. The blunted prolactin response to m-CPP appears to be the result of severe traumatization and independent of the BPD diagnosis.

Long-lasting effects of (+/-)3,4-methylenedioxymethamphetamine (ecstasy) on serotonin system function in humans

BACKGROUND

Fifteen (+/-)3,4-Methylenedioxymethamphetamine (MDMA) users, who did not show other drug dependencies or prolonged alcohol abuse, and 15 control subjects were included in the study.

METHODS

Prolactin (PRL) and cortisol (CORT) responses to the serotonergic agonist d-fenfluramine (D-fen), clinical psychobehavioral changes, and psychometric measures were evaluated 3 weeks and then 12 months after MDMA discontinuation.

RESULTS

MDMA users showed significantly reduced PRL and CORT responses in comparison with control subjects at 3 weeks (respectively, p < .001; p < .005). The responses of PRL to D-fen were unmodified at 12 months after prolonged abstinence and were significantly reduced in comparison with controls (p < .001). In contrast, CORT responses in MDMA users were restored after 12 months of abstinence, with significantly higher responses to D-fen, in comparison with 3-week responses (p < .05). MDMA users' high scores on the Novelty Seeking (NS) scale on the Tridimensional Personality Questionnaire (TPQ) appeared unchanged by long-term abstinence. In contrast, Buss Durkee Hostility Inventory (BDHI) (Buss and Durkee 1957) direct and guilt scores decreased significantly after 12 months of abstinence. PRL AUCs at 12 months were inversely correlated with the measures of MDMA exposure (r = -.538).

CONCLUSIONS

Our data indicate long-lasting 5-HT system impairment in abstinent MDMA users although the hypothesis of serotonergic changes attributable to a premorbid condition cannot be excluded. CORT restored responses to D-fen at 12 months, and the correlation of neuroendocrine changes with MDMA exposure suggest that the neuroendocrine impairment may be due to a partially reversible neurotoxic action of MDMA on the human brain.

The effect of ipsapirone and S(-)-pindolol on dopamine release in rat striatum and nucleus accumbens

Serotonin (5-hydroxytryptamine, 5-HT)(1A) receptor agonism and 5-HT(2A) receptor antagonism are components in the action of some of the recently developed antipsychotic drugs, e.g., clozapine and ziprasidone. However, studies of the role of 5-HT(1A) receptor agonism in the ability of these drugs to modulate dopamine (DA) release in the nucleus accumbens (NAC), which may be relevant to antipsychotic action, are lacking. Thus, we examined the effect of clinically available agents, ipsapirone, a 5-HT(1A) receptor partial agonist, and the mixed 5-HT(1A/1B)/beta receptor antagonist S(-)-pindolol, on DA release in the NAC compared to the striatum (STR). Ipsapirone produced a biphasic effect; low dose (0.1 mg/kg) decreased, high dose (3 mg/kg) increased and intermediate doses (0.1 and 1 mg/kg) did not change DA release in the NAC, respectively. However, ipsapirone, at all doses (0.3, 1, 3, but not 0.1 mg/kg) increased striatal DA release. S(-)-pindolol (3, 10, but not 1 mg/kg) produced a comparable increase in DA release in the NAC and STR. These results suggest that the ability of lower dose of ipsapirone to decrease DA release in the NAC is more likely to be due to 5-HT(1A) receptor agonism. On the other hand, the effect of higher dose of ipsapirone on striatal DA release may be due to 5-HT(1A) receptor antagonism, as is the case with S(-)-pindolol. The mechanism and clinical significance of these results for developing antipsychotic drugs is discussed.

Central serotonergic responsiveness in neurocardiogenic syncope: a clomipramine test challenge

BACKGROUND

Central serotonergic mechanisms appear to participate in the pathogenesis of recurrent neurally mediated syncope. The aim of the study was to investigate the responsiveness of the central serotonergic system by measuring the prolactin and cortisol responses to intravenous administration of the serotonin reuptake inhibitor clomipramine.

METHODS AND RESULTS

Twenty subjects free of any medical treatment were tested. Twelve had a history of recurrent syncopal attacks and positive tilt test (patient group, mean age 47+/-18 years, 8 men); 8 subjects without syncope and a negative tilt test result served as control subjects (mean age 49+/-10 years, 5 men). Twenty-five milligrams of clomipramine was administered intravenously within 15 minutes, and blood samples were taken at 0, 15, 30, 45, and 60 minutes. Two days later, a tilt test was performed at 60 degrees for 30 minutes and blood samples were taken at 0, 10, 20, and 30 minutes. During the clomipramine challenge, plasma prolactin levels increased in both groups. The levels at 30 minutes were higher in the patient group compared with the control group (17.3+/-7.2 vs 9.3+/-7.6 ng/mL, P=0.05). Similar results were observed for cortisol at 30 minutes (172+/-15 vs 118+/-21 ng/mL P=0. 04) and at 45 minutes (189+/-20 vs 116+/-23 ng/mL, P=0.03). The tilt test was positive in 8 (67%) out of 12 of the patient group and negative in all control subjects. In the samples taken during the tilt test, significant increases in prolactin and cortisol were observed only in the subjects with positive tilt test results.

CONCLUSIONS

Patients with a history of neurocardiogenic syncope show a higher responsiveness of the central serotonergic system to clomipramine challenge. The results support the view that central serotonergic mechanisms are involved in the pathophysiology of the syndrome.

Assessment of serotonergic function in major depression using d-fenfluramine: relation to clinical variables and antidepressant response

BACKGROUND

d-Fenfluramine, a specific serotonin (5-HT)-releasing agent without the catecholamine effects of d,l-fenfluramine, was used as a serotonergic neuroendocrine challenge in subjects with unipolar major depression.

METHODS

Patients were given 30 mg of d-fenfluramine orally, and prolactin and cortisol responses were measured over the following 5 hours. Endocrine responses were examined in relation to clinical variables and subsequent response to antidepressant treatment.

RESULTS

5-HT-mediated cortisol responses at baseline were inversely correlated with depression severity on the Montgomery Asberg Depression Rating Scale, Bech Melancholia Scale, and Clinical Global Impression scale. Prolactin responses were inversely correlated with anxiety on the Brief Symptom Inventory. A higher initial cortisol response to d-fenfluramine predicted a subsequent good antidepressant response.

CONCLUSIONS

We conclude that: a) the severity and symptom profile in major depression may be closely related to 5-HT dysfunction; and b) higher cortisol responses to d-fenfluramine predict a preferential response to treatment.

Diminished serotonin-mediated prolactin responses in nondepressed stroke patients compared with healthy normal subjects

BACKGROUND AND PURPOSE

The purpose of this study was to use hormonal responsiveness to d-fenfluramine (d-FEN) challenge as a measure of central serotonin (5-HT) function in a comparative evaluation of serotonergic abnormalities between stroke patients and healthy elderly normal subjects to test the hypothesis that stroke may be associated with diminished serotonergic functioning.

METHODS

Eight nondepressed medically stable stroke patients and 12 healthy volunteers completed a single-blind, placebo-controlled, fixed-order, crossover design challenge test with 30 mg of oral d-FEN. Baseline prolactin (PRL) and cortisol (CORT) and hormonal responses to d-FEN and placebo were measured at hourly intervals over a 4-hour period. Cardiovascular responses (pulse and blood pressure) and behavioral responses were also recorded at the same time points.

RESULTS

The 2 groups were comparable in demographics, body weight, plasma drug concentration, and behavioral and CORT responses. A 3-way ANOVA for repeated measures showed group differences for baseline adjusted PRL responses (change of scores from baseline). Peak PRL responses (maximal PRL change from baseline scores after treatment with d-FEN) in nondepressed stroke patients were attenuated compared with healthy elderly subjects, suggesting diminished serotonergic responsiveness in stroke patients.

CONCLUSIONS

The demonstrated serotonergic hypofunctioning poststroke may contribute to the high incidence of depressive disorders in stroke patients. Serotonergic agents may have a role in augmentation of stroke recovery.

Psychoneuroendocrinology of depression. Prolactin

Prolactin provides us with a window to the brain in our quest for understanding the psychobiology of depression, since the regulation of its release involves some of the monamine neurotransmitter systems that have been implicated in the pathophysiology of depression. Investigation examining basal prolactin plasma concentrations in depressed patients, including assessments of the rhythm of prolactin release, have not provided clear, consistent findings. Further exploration of the precise mechanisms involved in serotonin-stimulated prolactin release should shed light on the pathophysiology of abnormal prolactin responsivity in depression, and by extension, the psychobiologic basis of depression.

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

Three central indices of serotonin (5-HT) 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 assaultiveness (Buss-Durkee 'Assault') in personality-disordered individuals. Cerebrospinal fluid (CSF) 5-hydroxyindoleacetic acid (5-HIAA) concentration and prolactin responses to m-chlorophenylpiperazine (m-CPP) m-CPP (PRL[m-CPP]) and fenfluramine (PRL[FEN]), served as indices of pre-, post- and 'net'-synaptic central 5-HT activity, respectively. PRL[D,L-FEN] responses were inversely related to CSF 5-HIAA concentration and positively correlated with PRL[m-CPP] responses. Both PRL[D,L-FEN] and PRL[m-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.

Effects of trazodone and fluoxetine in the treatment of major depression: therapeutic pharmacokinetic and pharmacodynamic interactions through formation of meta-chlorophenylpiperazine

It has been suggested that (1) the clinical efficacy of the heterocyclic antidepressant trazodone in depression may, in part, be attributed to its metabolite meta-chlorophenylpiperazine (mCPP); and (2) the enhancement of the efficacy of trazodone by the addition of fluoxetine, a selective serotonin reuptake inhibitor, may, in part, be ascribed to fluoxetine-induced plasma concentrations of trazodone. After a washout period of 10 days, 27 inpatients with major depression were treated with trazodone 100 mg/day (orally). One week later (T0), fluoxetine 20 mg/day, placebo, or pindolol 7.5 mg/day was added. Plasma concentrations of mCPP and trazodone were determined at T0 and 2 and 4 weeks later. Although placebo pindolol had no significant effect on the plasma concentrations of mCPP and trazodone, there was a significant increase of the concentrations of these compounds associated with the combination of trazodone + fluoxetine. The results suggest that fluoxetine-induced increases in plasma mCPP and trazodone concentrations contribute to the clinical efficacy of the combination of fluoxetine + trazodone. It is suggested that desensitization of 5-HT2C receptor function by mCPP as well as fluoxetine may contribute to the antidepressant effects of this combination.

Effect of sleep deprivation on neuroendocrine response to a serotonergic probe in healthy male subjects

Neuroendocrine responses to stimulation with a selective serotonin reuptake inhibitor (citalopram) were measured to investigate the effects of all-night sleep deprivation on serotonergic function in healthy male subjects (n = 7). We studied citalopram-stimulated prolactin and cortisol plasma concentrations in a placebo-controlled cross-over protocol following sleep and sleep deprivation. Citalopram infusion (20 mg i.v. at 14:20-14:50 h) after a night of undisturbed sleep prompted robust increases in both plasma prolactin and cortisol concentrations. Following a night of sleep deprivation, by contrast, the citalopram-induced prolactin response was blunted, but the cortisol response was not significantly altered. This differential response pattern relates to the distinct pathways through which serotonin may activate the corticotrophic and the lactotrophic systems. While an unchanged cortisol response does not indicate (but also does not refute the possibility of) an altered serotonergic responsivity following sleep deprivation, the suppressed prolactin response could reflect a downregulation of 5-HT1A or 2 receptors. An alternative, not mutually exclusive, explanation points to the possibility that sleep deprivation activates the tubuloinfundibular dopaminergic system, the final inhibitory pathway of prolactin regulation.

Efficacy of treatment with trazodone in combination with pindolol or fluoxetine in major depression

Fluoxetine, a selective serotonin (5-HT) reuptake inhibitor (SSRI), and trazodone, a heterocyclic antidepressant, are effective in the treatment of major depression and treatment resistant depression (TRD). Chronic treatment with both drugs causes increases in extracellular 5-HT through 5-HT reuptake inhibition and desensitization of inhibitory 5-HT1A autoreceptors. It has been shown that pindolol, a serotonin (5-HT)1A-receptor antagonist, may shorten the latency of onset of SSRIs in depression. The aim of the present study was to examine whether pindolol may increase the efficacy of a subtherapeutical dosage of trazodone in the treatment of major depression and TRD, defined according to the Thase and Rush criteria (1995). Thirty-three major depressed inpatients of whom 26 with TRD participated in this study. Ten days after hospitalization, treatment with trazodone 100 mg/day was started. After 1 week trazodone treatment, patients were randomized-using a double blind placebo controlled design-to receive trazodone 100 mg/day+placebo; trazodone 100 mg/day+pindolol 7.5 mg/day: or trazodone 100 mg/day+fluoxetine 20 mg/day and treated during 4 weeks. The 17-item Hamilton Depression Rating Scale (HDRS) was used as outcome measure. It was found that trazodone+pindolol was as effective as trazodone+fluoxetine in the treatment of major depression and TRD and significantly more effective than trazodone+placebo. Using an outcome measure of 50% reduction in the HDRS, we found that 72.5% of the depressed patients treated with trazodone+pindolol and 75% of depressed patients treated with trazodone+fluoxetine showed a clinically significant response compared with 20.0% of trazodone+placebo-treated patients.

Effects of meta-chlorophenylpiperazine on neuroendocrine and behavioral responses in male schizophrenic patients and normal volunteers

Functional alterations in the central serotonergic system, including presynaptic and postsynaptic function, have been reported in schizophrenia. Recently, there have been conflicting reports that the increase in plasma cortisol or prolactin concentrations induced by meta-chlorophenylpiperazine (mCPP) was significantly blunted in schizophrenic patients compared with normal volunteers. Studies of the behavioral effects of mCPP, a serotonin (5-HT) receptor partial agonist with high affinity for 5-HT1C binding sites, have also yielded conflicting results in schizophrenic patients. The purpose of this study was to examine plasma levels of prolactin and cortisol, body temperature, and behavioral responses to mCPP and placebo in a single-blind study in 25 schizophrenic and 15 normal men. No differences either between schizophrenic patients and normal volunteers or between paranoid and undifferentiated/residual subtypes of schizophrenia were found in mCPP-induced prolactin, cortisol, or temperature responses. Schizophrenic patients and normal volunteers reported significant increases in feeling calm and feeling strange of comparable magnitude following mCPP. No significant differences between normal volunteers and schizophrenic patients were found in post-mCPP behavioral ratings, such as anxiety, irritability, depression, restlessness, or arousal.