Autoradiographic demonstration of increased serotonin 5-HT2 and beta-adrenergic receptor binding sites in the brain of suicide victims

Morphometric methods for studying the prefrontal cortex in suicide victims and psychiatric patients

Neurochemical studies demonstrate altered numbers of monoaminergic receptors in the prefrontal cortex in suicide and depression victims, implicating dysfunction of the prefrontal cortex in the neuropathology of suicide and psychiatric disorders. Neuroimaging studies in vivo have revealed an altered pattern of cortical metabolism and reductions in frontal lobe volume in patients with schizophrenia (SCZ) or depression. However, the precise morphopathology underlying these abnormalities and their relevance to suicide are unknown. Our recent three-dimensional cell counting of dorsolateral prefrontal cortex from 16 postmortem SCZ brains (10 suicide completers) revealed cellular changes (increased neuronal density, and reduced laminar width and neuronal size) that may be associated with neuroimaging observations. Evaluation of the same morphometric parameters in the prefrontal cortex in seven bipolar brains (three committed suicide) revealed similarities (decreased cortical and laminar thickness) and differences (unchanged overall neuronal density and laminar densities) between morphopathology of SCZ and bipolar disorder. In another population of suicide victims with major depression (nonpsychotic), further morphopathological differences from SCZ and similarities to bipolar disorder were observed in the prefrontal cortex. From these data we can conclude that the morphopathology observed in brain tissue from suicide victims appears to vary based on psychiatric symptomatology. In order to confirm this hypothesis and to establish the specificity of morphometric findings in relation to psychiatric disorders and suicide, additional studies are warranted in nonsuicide subjects with SCZ, major depression, or bipolar disorder.

Altered serotonin function in suicide. Evidence from platelet and neuroendocrine studies

Significant progress has been made in understanding psychosocial, psychological, and environmental factors associated with suicide; however, it is only recently that attention has been paid to the understanding of the neurobiology of suicide. There are several studies that implicate the serotonin (5-HT) system in suicide. Initial evidence was obtained from observations of low 5-hydroxyindoleacetic acid (5-HIAA) in cerebrospinal fluid (CSF) of depressed patients with a previous history of suicide attempts. Several strategies have been used to examine the serotonergic system in suicidal behavior, which include the determination of serotonin and its metabolites in CSF and postmortem brain tissues as well as serotonin receptor subtypes in postmortem brain tissues, and in platelets of suicidal patients. The neuroendocrine strategy, often termed the "window to the brain," has been extensively used for studying the serotonergic system in suicide. This chapter will review the results obtained from neuroendocrine and serotonin studies in platelets. Initial studies in platelets focussed on determining serotonin uptake and serotonin transporter binding sites in platelets of depressed and suicidal patients. Whereas several studies have found decreased imipramine binding sites of platelets of depressed patients, imipramine binding sites in platelets of suicidal patients showed inconsistent results. Similarly, no consistent changes in 5-HT uptake have been observed in platelets obtained from suicidal patients compared to nonsuicidal patients. On the other hand, studies of platelet 5-HT2A receptors appear to be quite encouraging. Initially, several investigators indicated that they found an increase in platelet 5-HT2A receptors in depressed patients. Subsequently, it was shown that platelet 5-HT2A receptors in suicidally depressed patients were significantly higher compared to nonsuicidally depressed patients and normal control subjects. It has also been shown that platelet 5-HT2A receptors are increased in suicidal patients independent of diagnosis, similar to platelets. 5-HT2A receptors have also been shown to be increased in the postmortem brain of suicide victims by several investigators, although some investigators do not find such an increase. The neuroendocrine strategy provides an important method for studying serotonin function in the central nervous system of depressed and suicidal patents. Using a serotonergic probe of 5-HT1A receptors, several investigators examined ipsapirone-induced prolactin release in suicidal patients and did not find it different that that of control subjects. On the other hand, fenfluramine, which causes release of serotonin and blocks serotonin uptake, causes a decreased release of prolactin in depressed patients compared to normal control subjects. Furthermore it has been shown by some investigators that fenfluramine-induced prolactin release is also decreased in suicidal patients compared to normal control subjects. In summary, platelet and neuroendocrine studies have provided initial evidence sufficient to suggest serotonergic abnormalities in suicidal patients. Most earlier evidence is based on CSF 5-HIAA studies, but it appears that 5-HT2A receptors in both platelet and postmortem brain samples are increased in suicidal patients. The observation that platelet 5-HT2A receptors are increased in suicidal patients independent of diagnosis provides a very useful potential biological marker for identifying suicidal patients.

Neurobiology of serotonin in depression and suicide

Alterations in serotonin neurotransmission have been implicated in the pathophysiology of major depression and suicide. However, a clear picture of serotonergic abnormalities has not emerged from postmortem studies of depression and suicide. In suicide victims with major depression and psychiatrically normal control subjects, we have examined various indices of serotonergic neurotransmission in axonal projection areas such as prefrontal cortex and hippocampus, and cell bodies of origin within the dorsal raphe nucleus (DR). Although there were no significant differences between suicide victims with major depression and psychiatrically normal control subjects in serotonin-1A or serotonin-2A receptors in the right prefrontal cortex (area 10) or the hippocampus, there were region-specific alterations in suicide victims with major depression in G-protein-induced activation of the phosphoinositide signal transduction system and in the levels of G-protein alpha subunits involved in cyclic AMP synthesis. A pilot study examining the ventrolateral subnucleus of the DR (DRvl) reveals that serotonin-1A receptors are increased in suicide victims with major depression as compared to normal control subjects. Altered signal transduction in cerebral cortex and altered regulation of serotonin neurons in the DR may be important in the pathophysiology of major depression and suicide.

Low central nervous system serotonergic activity is traitlike and correlates with impulsive behavior. A nonhuman primate model investigating genetic and environmental influences on neurotransmission

We have used nonhuman primates to examine developmental and behavioral correlates of CNS serotonergic activity, as measured by concentrations of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the cerebrospinal fluid (CSF). These studies show that interindividual differences in CNS serotonin turnover rate exhibit traitlike qualities and are stable across time and settings, with interindividual differences in CSF 5-HIAA concentrations showing positive correlations across repeated sampling. Primates with low CNS serotonergic activity exhibit behaviors indicative of impaired impulse control, unrestrained aggression, social isolation, and low social dominance. Maternal and paternal genetic influences play major roles in producing low CNS serotonin functioning, beginning early in life. These genetic influences on serotonin functioning are further influenced by early rearing experiences, particularly parental deprivation.

Pathophysiology of the locus coeruleus in suicide

Clinical and basic research findings implicate a role for brain norepinephrine in the pathophysiology of psychiatric disorders that can lead to suicide. However, the precise biological abnormality of neurons that produce norepinephrine in the brain in these disorders has not been elucidated. We have studied the biochemistry of the locus coeruleus (LC), the principal source of brain norepinephrine, from suicide victims and from age-matched, natural or accidental death control subjects. Levels of tyrosine hydroxylase (rate-limiting enzyme in norepinephrine biosynthesis) and amounts of binding to a2 adrenoceptors (norepinephrine receptors) are elevated in the LC of suicide victims as compared to control subjects. These biological abnormalities in the LC from suicide victims are very similar to biochemical changes observed in the rat LC following repeated exposure to environmental stimuli that activate the LC or to treatment with pharmacological agents that deplete brain norepinephrine. It is hypothesized that persons who commit suicide have experienced chronic activation of the LC, resulting in depletion of synaptic norepinephrine and compensatory changes in concentrations of noradrenergic proteins.

Regulation of 5-HT receptors and the hypothalamic-pituitary-adrenal axis. Implications for the neurobiology of suicide

Disturbances in the serotonin (5-HT) system is the neurobiological abnormality most consistently associated with suicide. Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis is also described in suicide victims. The HPA axis is the classical neuroendocrine system that responds to stress and whose final product, corticosteroids, targets components of the limbic system, particularly the hippocampus. We will review results from animal studies that point to the possibility that many of the 5-HT receptor changes observed in suicide brains may be a result of, or may be worsened by, the HPA overactivity that may be present in some suicide victims. The results of these studies can be summarized as follows: (1) chronic unpredictable stress produces high corticosteroid levels in rats; (2) chronic stress also results in changes in specific 5-HT receptors (increases in cortical 5-HT2A and decreases in hipocampal 5-HT1A and 5-HT1B); (3) chronic antidepressant administration prevents many of the 5-HT receptor changes observed after stress; and (4) chronic antidepressant administration reverses the overactivity of the HPA axis. If indeed 5-HT receptors have a partial role in controlling affective states, then their modulation by corticosteroids provides a potential mechanism by which these hormones may regulate mood. These data may also provide a biological understanding of how stressful events may increase the risk for suicide in vulnerable individuals and may help us elucidate the neurobiological underpinnings of treatment resistance.

Neuropathology of suicide. A review and an approach

Neuropathology is one approach to the effort to elucidate the pathophysiology of suicide. Initial neurochemical studies focusing on the roles of serotonin (5-HT) and noradrenaline (NE) abnormalities in brains of suicide victims have been somewhat inconsistent. More recently developed methodologies, including quantitative receptor autoradiography, immunoblotting, immunohistochemistry, cell morphometry, in situ hybridization, Northern analysis, solution hybridization/RNase protection assay, reverse transcriptase polymerase chain reaction, and genotyping, which have already been applied successfully in studies of other disorders of brain structure or function, are now increasingly being adopted for postmortem studies of suicide. These new strategies are adding convergent evidence for brain 5-HT and NE dysfunction in the etiology of suicide susceptibility, refining the neuroanatomical localization of this dysfunction, and in addition, implicating heretofore unsuspected candidate neurotransmitter systems in the neuropathological substrates of suicide susceptibility. It is argued here that the confluence of the availability of suitable postmortem samples and this augmentation of our armamentarium of techniques promises the attainment of important new insights into the biological underpinnings of suicide from postmortem research. It is to be hoped that this new knowledge might inspire novel pharmacotherapeutic strategies for the prevention of suicide.

Postmortem findings in suicide victims. Implications for in vivo imaging studies

Alterations in serotonergic and noradrenergic receptor binding in membrane homogenates from the brain of suicide victims suggest a biological substrate for the vulnerability to commit suicide. We and others have employed high-resolution quantitative autoradiography of full coronal sections of the prefrontal cortex to map the locus of maximal change in receptor binding. We found alterations in binding to the serotonin transporter, the 5-HT1A, and the 5-HT2A receptors primarily in the ventral and ventrolateral prefrontal cortex of suicide victims. Importantly, these changes are often modest in magnitude and anatomically restricted to one or two Brodmann areas. Furthermore, we have found that care in case selection is essential, because sex, age, drugs, and comorbid diagnoses contribute to receptor binding. The implications for in vivo imaging are considerable, directing the focus of such studies toward the ventrolateral prefrontal cortex. However, because ligands are limited, as is the resolution of current methods, including PET, automated analyses that produce statistical images, rather than manual selection of individual slices, will likely lack the ability to detect the discrete receptor changes found postmortem. Alternatively, the advantages of examining large numbers of subjects, imaging the entire brain, obtaining detailed clinical information in the living patient, and magnifying the changes with neuropharmacological challenges present a promising outlook for making major advances into the identification of brain abnormalities associated with suicide risk.

Subsensitivity of adenylyl cyclase-coupled receptors on mononuclear leukocytes from drug-free inpatients with a major depressive episode

Previous studies have demonstrated blunted beta-adrenergic responsivity in leukocytes from depressed patients. We sought to determine if this blunted cyclic adenosine monophosphate (AMP) response is specific for beta-adrenergic receptors (homologous), or whether other adenylyl cyclase-coupled receptors are also involved (heterologous), in order to localize this effect at the level of the receptor versus the coupling protein or the transducer, adenylyl cyclase. We studied adenylyl cyclase-mediated responses in peripheral blood mononuclear cells from 95 drug-free patients with a major depressive episode and 69 healthy controls. We found a similar degree of decrease in the peak cyclic AMP response to activation of the beta-adrenergic receptor (28%) and the prostaglandin receptor (34%) in the depressed patients, which indicated heterologous desensitization. Forskolin cyclic AMP responses were not blunted. Blunting of cyclic AMP responses to isoproterenol did not appear to correlate with levels of plasma norepinephrine and epinephrine or hypothalamic-pituitary-adrenocortical function. The absence of a decrease in the peak forskolin-generated cyclic AMP response, which involves direct activation of adenylyl cyclase, suggests an abnormality at the level of the coupling protein in these adenylyl-coupled receptors in depressed patients. Future studies need to determine whether this leukocyte signal transduction defect in depression also involves brain adenylyl cyclase-coupled receptors.

Biologic alterations in the brainstem of suicides

This article reviews the data supporting the notion that there are alterations in serotonin and norepinephrine in the ventral prefrontal cortex and brainstem of suicide victims. Normal amounts of serotonin are found in terminal fields such as the dorsolateral prefrontal cortex, but serotonin responses are defective at least in the hypothalamus. Suicide victims appear to have fewer noradrenergic LC neurons, containing more of the tyrosine hydroxylase enzyme needed for transmitter synthesis. A failure of behavior restraint mechanisms involving the prefrontal cortex as a consequence of alterations in brainstem monoaminergic nuclei may result in a predisposition to suicidal behavior.

Identification of suicide risk factors using epidemiologic studies

Suicide is a complex outcome of multiple, inter-related factors. This article presents the epidemiology of completed and attempted suicide and discusses the known risk factors for suicide within a framework designed to encourage a systematic approach to theory testing and prevention. Mental and addictive disorders, frequently in co-occurrence, are the most powerful risk factors for suicide in all age groups, accounting for over 90 percent of all completed suicides. In combination with proximal risk factors such as access to firearms or other lethal means, recent and severe stressful life events, and intoxication, they can form the necessary and sufficient conditions for suicide.

Effects of corticosterone on 5-HT1A and 5-HT2 receptor binding and on the receptor-mediated behavioral responses of rats

The effects of corticosterone after binding to 5-HT1A and 5-HT2 receptors were studied in rats. Binding of [3H]8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) to 5-HT1A receptors in the hippocampus decreased 24 h after both acute and chronic (14 day) administration of CORT (50 mg/kg, s.c.). Chronic, but not acute, CORT treatment increased [3H]ketanserin binding to 5-HT2 receptors in the frontal cortex. Receptor-mediated behavioral responses were also examined following acute and chronic CORT treatment. Flat body posture and hypothermia induced by 8-OH-DPAT, a 5-HT1A receptor agonist, were attenuated following chronic, but not acute, CORT administration. (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), a 5-HT2 receptor agonist, induced wet-dog shakes, but not hyperthermia and this response was increased 24 h after the chronic administration of CORT. These findings indicate that both 5-HT1A and 5-HT2 receptor functions were changed following chronic exposure to high levels of CORT. Such changes in these receptor systems may play an important role in the etiology of affective disorders.

[3H]ketanserin binding in human brain postmortem

This study aimed at comparing the binding characteristics of [3H]ketanserin, a high-affinity serotonin 2A (5-HT2A) receptor antagonist, in the prefrontal cortex, hippocampus and striatum of human brain post-mortem. The results indicated the presence of a single population of binding sites in all the regions investigated, with no statistical difference in maximum binding capacity (B(max)) or dissociation constant (K(d)) values. The pharmacological profile of [3H]ketanserin binding was consistent with the labeling of the 5-HT2A receptor, since it revealed a competing drug potency ranking of ketanserin = spiperone > clozapine = haloperidol > methysergide > mesulergine > 5-HT. In conclusion, the 5-HT2A receptor, as labeled by [3H]ketanserin, would seem to consist of a homogenous population of binding sites and to be equally distributed in human prefronto-cortical, limbic and extrapyramidal structures.

Serotonergic, noradrenergic, and dopaminergic measures in suicide brains

Concentrations of the three main monoamines (5-HT, NA, and DA), their metabolites (5-HIAA, DOPAC, and HVA), and the serotonin precursor 5-hydroxy-L-tryptophan were simultaneously measured in frontal cortex, gyrus cinguli, and hypothalamus from 23 controls and 18 suicide victims. Overall suicides did not show significant differences with respect to the control group in any of the measured compounds. Significant increases in noradrenaline and dopamine concentrations were noted in the carbon monoxide poisoning suicides, together with a significant increased hypothalamic dopamine in the drug overdose suicides. It is suggested that the suicidal behavior is not related to substantial changes in cortical and hypothalamic monoaminergic function; however, the reported results could be secondary to the rapid effect of hypoxia and of the acute self-administration of certain drugs in specific metabolic pathways.

Platelet serotonergic indices in major depression: up-regulation of 5-HT2A receptors unchanged by antidepressant treatment

This study examined, in the largest sample of major depressives reported so far, platelet serotonergic parameters (5-HT uptake, [3H]paroxetine binding and 5-HT2A receptors measured by [3H]LSD binding) in 60 antidepressant-free depressed patients and 40 age- and gender-matched control subjects before treatment, and in 45 major depression patients during treatment with antidepressants. We found that, at baseline, the density (Bmax) of 5-HT2A receptors was significantly higher (by 39%) in depressed patients than in controls. Suicidal patients had significantly higher Bmax values than controls or non-suicidal patients. The rate of serotonin uptake (Vmax), but not the uptake at a single concentration, was significantly higher in depressed patients, particularly in females. There was no significant difference between the Kd or Bmax of [3H]paroxetine binding in control and depressed subjects. Treatment with antidepressant drugs of different pharmacological profile had no significant effect on the density of 5-HT2A receptors, nor did the receptor number predict the response to treatment. The affinity of serotonin uptake site for 5-HT and [3H]paroxetine significantly decreased during treatment with antidepressants, particularly SSRIs. Suppression of 5-HT uptake correlated with decreases in Hamilton depression (HAMD) scores. Our data suggest that the increased density of platelet 5-HT2A receptors may be associated with untreated major depression in antidepressant-free depressed patients, in particular those with suicidal thoughts. The persistence after antidepressant treatment and clinical improvement would suggest that up-regulation of 5-HT2A receptors is a trait rather than state phenomenon. Correlation of 5-HT uptake suppression with decreases in HAMD scores suggests that serotonin uptake inhibition is a relevant factor in antidepressant drug effect and clinical improvement.

Cerebrospinal fluid amines and higher-lethality suicide attempts in depressed inpatients

Previous studies have found that not all suicide attempters with major depression have reduced serotonergic activity based on low cerebrospinal fluid 5-hydroxyindoleacetic acid (CSF- 5-HIAA) levels. In this study we hypothesized that serotonergic function is lower in depressed patients who have carried out high-lethality suicide attempts resulting in more medical damage, which might explain differences in serotonergic activity among depressed suicide attempters. We assessed the relationship of CSF 5-HIAA and other amine metabolites to the most lethal lifetime suicide attempt in 22 drug-free inpatients with major depression. CSF 5-HIAA levels were lower in depressed patients with a history of a high-lethality or well-planned suicide attempt compared to depressed patients with a history of only low-lethality suicide attempt(s). Other CSF monoamine metabolites did not correlate with suicidal behavior. Low serotonergic activity may correlate with a predisposition to more lethal suicide attempts in major depression.

Differential age-related loss of pigmented locus coeruleus neurons in suicides, alcoholics, and alcoholic suicides

We previously reported fewer locus coeruleus (LC) neurons in both suicide victims and alcoholics than among a group of nonpsychiatric controls. In the present paper we examine the rate of decline in the number of LC neurons with age, looking for possible differential rates among suicide victims, alcoholics, and controls. We also compare these groups with a group of alcoholics who died by suicide, and consider the effects of sex, race, and postmortem interval. LC neuron counts were obtained from a total of 32 subjects. In all groups, the number of neurons decreased with age, but by roughly age 40 the average LC count among the three suicide and/or alcoholic groups was lower than among controls. The rate of LC neuron loss was greater among suicides than among controls, but the rate of loss among alcoholics who were at least 30 years old was the same as that among the controls. Our group of alcoholic suicides had counts that were statistically indistinguishable from those of suicides. Differences among groups appear to be most pronounced in the middle third of the LC. Further studies are needed to determine the mechanisms of noradrenergic neuron loss and whether it is associated with an underlying major depression in suicide victims, or acquired after a period of excessive alcohol consumption.

Decreased frontal cortical serotonin2A receptors in schizophrenia

5HT2A receptors were measured in the frontal cortex from schizophrenic and non-schizophrenic subjects. There was a decrease in the density of 5HT2A receptors in Brodmann's areas 8, 9 and 10 from the schizophrenic subjects. In addition, there was an age-dependent decrease in the density of 5HT2A receptors in Brodmann's areas 9 from the non-schizophrenic subjects, which was absent in the schizophrenic subjects. Available evidence does not suggest that the change in 5HT2A receptors in the schizophrenic subjects was a result of drug treatment before death. These data may indicate that decreased 5HT2A receptors in the frontal cortex are involved in the pathology of schizophrenia.

Platelet serotonergic markers and Tridimensional Personality Questionnaire measures in a clinical sample

A group of patients with major depressive disorder, with and without comorbid obsessive-compulsive disorder, completed the Tridimensional Personality Questionnaire (TPQ). Harm Avoidance scores were found to be high compared to published age-matched norms and to display a significant positive correlation with Hamilton Depression Rating Scale scores. Platelet 125I-lysergic acid diethylamide (125I-LSD) and 3H-paroxetine binding Bmax values were measured to test Cloninger's hypothesis that Harm Avoidance scores would correlate significantly with measures of serotonergic function. A significant inverse correlation was found between Harm Avoidance scores and 125I-LSD Bmax values. Correlations between 3H-paroxetine Bmax values and TPQ scale scores were not significant. These results suggest an alternative view of the literature relating platelet 5-hydroxytryptamine-2a receptors and mood disorders in that the temperament dimension, Harm Avoidance, may explain prior inconsistencies involving links with depression and suicidality.

Potential animal model of multiple chemical sensitivity with cholinergic supersensitivity

Multiple Chemical Sensitivity (MCS) is a clinical phenomenon in which individuals, after acute or intermittent exposure to one or more chemicals, commonly organophosphate pesticides (OPs), become overly sensitive to a wide variety of chemically-unrelated compounds, which can include ethanol, caffeine and other psychotropic drugs. The Flinders Sensitive Line (FSL) rats were selectively bred to be more sensitive to the OP diisopropylfluorophosphate (DFP) compared to their control counterparts, the Flinders Resistant Line (FRL) rats. The present paper will summarize evidence which indicates that the FSL rats exhibit certain similarities to individuals with MCS. In addition to their greater sensitivity to DFP, the FSL rats are more sensitive to nicotine and the muscarinic agonists arecoline and oxotremorine, suggesting that the number of cholinergic receptors may be increased, a conclusion now supported by biochemical evidence. The FSL rats have also been found to exhibit enhanced responses to a variety of other drugs, including the serotonin agonists m-chlorophenylpiperazine and 8-OH-DPAT, the dopamine antagonist raclopride, the benzodiazepine diazepam, and ethanol. MCS patients report enhanced responses to many of these drugs, indicating some parallels between FSL rats and MCS patients. The FSL rats also exhibit reduced activity and appetite and increased REM sleep relative to their FRL controls. Because these behavioral features and the enhanced cholinergic responses are also observed in human depressives, the FSL rats have been proposed as a genetic animal model of depression. It has also been reported that MCS patients have a greater incidence of depression, both before and after onset of their chemical sensitivities, so cholinergic supersensitivity may be a state predisposing individuals to depressive disorders and/or MCS. Further exploration of the commonalities and differences between MCS patients, human depressives, and FSL rats will help to elucidate the mechanisms underlying MCS and could lead to diagnostic approaches and treatments beneficial to MCS patients.

Zalospirone in major depression: a placebo-controlled multicenter study

Compounds active at the serotonin (5-HT)1A receptor (mostly azapirones) have shown some evidence of antidepressant effect. We report here the results of an antidepressant trial with zalospirone, a novel cyclic imide with 5-HT1A partial agonist activity. Two hundred eighty-seven outpatients (mean age 44 years, 55% men, 45% nonfertile women) who met criteria for unipolar major depression with a minimum 21-item Hamilton Rating Scale for Depression (HAM-D) score of 20 were randomly assigned to receive 6 weeks of double-blind treatment with either placebo or one of three fixed doses of zalospirone (6, 15, or 45 mg/day), administered three times daily. The high dose (45 mg) of zalospirone produced a significant antidepressant effect compared with placebo from week 2 on with mean improvement (change from baseline) in HAM-D total score of 12.8 versus 8.4 (p < 0.05) at week 6. Clinical improvement with the high dose of zalospirone was consistent across all outcome measures, however, only in the observed cases and not the last-observation-carried-forward analyses. Improvement with the 6-mg or 15-mg doses was greater than that with placebo, but not significantly so, suggesting a dose-response effect. Although the 45-mg dose of zalospirone seemed to have significant antidepressant efficacy, it was not well tolerated. Dizziness and nausea were noted in almost half of the patients, and by week six, 51% of patients in the high-dose group had dropped out. Whether or not tolerance to this high dose might be improved by gradual drug titration, only future research can answer.

Positron emission tomographic imaging of serotonin activation effects on prefrontal cortex in healthy volunteers

Serotonergic system abnormalities have been implicated in major depression, suicide, violence, alcoholism, and other psychopathologies. The prolactin response to fenfluramine has been widely used as a neuroendocrine probe to study brain serotonin responsivity. We have extended this methodology by using the positron emission tomography (PET) 18F-fluorodeoxyglucose (18FDG) method to examine the fenfluramine-induced changes in regional cerebral glucose metabolism (rCMRglu), an indicator of changes in regional neuronal activity. We report results on 16 healthy controls, each of whom underwent two PET studies. One group of six subjects had a placebo on day 1 and a single 60 mg oral dose of fenfluramine on day 2. The second group, of 10 subjects, was tested on two consecutive occasions without drug or placebo. Data were analyzed for significant rCMRglu changes on day 2 vs day 1 using the statistical parametric mapping method (p < 0.01). Subjects who did not receive drugs showed no statistically significant areas of rCMRglu increase or decrease on day 2 versus day 1. In contrast, the group that received fenfluramine showed significant fenfluramine-induced responses. Areas of rCMRglu increases involved mainly the left prefrontal and left temperoparietal cortex. Within the prefrontal cortex, two major areas of rCMRglu increase included, first, an area centered on the anterior cingulate and, second, an area in the lateral prefrontal cortex involving principally the inferior, middle, and superior frontal gyri. Some decreases in rCMRglu were observed, principally in the right hemisphere. This PET-fenfluramine paradigm is a potentially useful method for studying abnormalities of serotonin function in the prefrontal cortex.

Desipramine administration in the olfactory bulbectomized rat: changes in brain beta-adrenoceptor and 5-HT2A binding sites and their relationship to behaviour

1. The effects of repeated administration of the tricyclic antidepressant drug, desipramine (DMI), on behaviour (locomotor activity and rearing) and the number and affinity of brain beta-adrenoceptor and 5-HT2A receptor binding sites were examined in olfactory bulbectomized (OB) and sham-operated control rats. 2. Locomotor activity and rearing were increased in OB rats compared to sham-operated controls. The effect of various doses of DMI (administered orally twice daily for 21 days) on these behavioural measures was examined. A dose of 7.5 mg kg-1 provided optimal reversal of hyperlocomotion and increased rearing in OB rats, without changing these measures in sham-operated controls. 3. The time course of DMI (7.5 mg kg-1) on behavioural and neurochemical measures was examined. locomotion and rearing in OB rats were not significantly altered after 7 days, were significantly attenuated after 14 days and were normalized after 21 days. 4. After 7 days of DMI administration the number of beta-adrenoceptors was lower in frontal and occipital cortex and hippocampus. This reduction was largely restricted to the beta 1-adrenoceptor subtype. Administration of DMI for 14 or 21 days did not further reduce the number of beta-adrenoceptors. The DMI induced reduction in beta-adrenoceptors did not differ in OB and sham-operated control rats. 5. DMI administration for up to 21 days produced a progressive reduction in the number of 5-HT2A receptors in frontal cortex, without significant alterations in occipital cortex. 6. The time course of the reduction in the number of 5-HT2A receptors was similar to that of the DMI-induced behavioural changes whereas that for the reduction in beta-adrenoceptors was clearly different. 7. The present results suggest that the action of DMI in this animal model is unlikely to be directly related to a reduction in beta-adrenoceptors but may be related to a reduction in frontal cortical 5-HT2A receptors.

Indices of brain beta-adrenergic receptor signal transduction in the learned helplessness animal model of depression

Both stress response and antidepressant drug action may be mediated by beta-adrenergic receptors (beta AR). Since learned helplessness is a stress-induced animal model of depression, beta AR are relevant to investigate in this model. To date, studies have measured changes in total receptor density (RT), but have not examined more detailed aspects of signal transduction mechanisms such as coupling of the receptor to GS protein. We have investigated brain beta AR coupling in the frontal cortex, hippocampus and hypothalamus of rats exposed to inescapable shock and then tested for learned helplessness, and in both tested and naive controls using [125I]-iodocyanopindolol (ICYP) as the ligand. Both antagonist-saturation and agonist-displacement experiments were conducted, and the specificity for the beta AR was optimized by excluding ICYP binding to 5HT1B receptors. The percentage receptor density in the high-conformational state (%RH) and the ratio of agonist (isoproterenol) dissociation constant from the receptor in the low-/high-conformational states (KL/KH) were used as indices of coupling to GS protein. No significant differences were found between rats developing learned helplessness and non-helpless rats after inescapable stress in any parameter measured in any brain region. In the frontal cortex, exposure to inescapable shock induced beta AR uncoupling from GS protein as suggested by a low KL/KH ratio both in helpless and non-helpless rats but not in either control group. In the hypothalamus, there were trends for higher RL, RT and KL/KH ratio in helpless rats and stressed controls compared to naive controls. These findings suggest that beta AR binding parameters in frontal cortex, hippocampus or hypothalamus did not differentiate between helpless and non-helpless rats. Changes in beta AR coupling observed in these brain regions may reflect effects of stress, which appeared to be region-specific, rather than stress-induced behavioral 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.

Transcranial magnetic stimulation downregulates beta-adrenoreceptors in rat cortex

Recently, a method for transcranial magnetic stimulation (TMS) of the brain has been developed. Thus, it is possible to explore neurochemical and behavioral effects of TMS in rats. Repeated TMS (9 days) reduced beta-adrenergic receptor binding in cortex, as does electroconvulsive shock (ECS) and other antidepressant treatments. Thus TMS appears to be a potential antidepressive treatment.

Beta-adrenergic receptor subtypes in human pineal gland

The secretion of melatonin by the pineal has been promoted as a direct monitor of adrenergic function in depressive illness. However, discrepant findings have been reported, possibly reflecting a complex adrenergic regulation of pineal output. In order to clarify the anatomical localization and relative density of beta-adrenergic receptors and their subtypes in human pineal, quantitative autoradiographic analysis was conducted of beta-adrenergic receptors in postmortem specimens using the high affinity radioligand 125I-pindolol. Dense specific binding was found throughout the gland. beta 1 -adrenergic receptors were more numerous, but beta 2-receptors were present in an overlapping anatomical distribution with beta 1-receptors.

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.

Chronic forced swim stress of rats increases frontal cortical 5-HT2 receptors and the wet-dog shakes they mediate, but not frontal cortical beta-adrenoceptors

We studied the effects of chronic forced swim stress on 5-HT2 receptors and beta-adrenoceptors in the rat frontal cortex. The number of 5-HT2 receptors was increased immediately after the last chronic stress, but not after an acute stress. In vivo, the number of wet-dog shakes induced by a 5-HT2 receptor agonist, (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), was increased 24 h after the last chronic stress. However, the concentrations of 5-HT and 5-hydroxyindole acetic acid (5-HIAA), measured by high pressure liquid chromatography (HPLC), were not altered by this stress. Binding sites for [3H]CGP-12177, i.e., beta-adrenoceptor sites, were unchanged after both the acute and the chronic stress. These results suggest that, in the rat, the chronic forced swim stress increases the number of frontal cortical 5-HT2 receptors and the number of wet-dog shakes mediated by these receptors, while the number of frontal cortical beta-adrenoceptors is not increased by this treatment.

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.

Serotonin-induced 5-HT1A receptor desensitization in C6BU-1 glioma cells transfected with 5-HT1A receptor gene

In this study, it has been clearly demonstrated that a selective 5-hydroxytryptamine (5-HT)1A agonist, 8-OH-2-(di-n-propylamino)-tetraline (8-OH-DPAT, 1 microM) significantly inhibited forskolin (10 microM)-stimulated cyclic AMP (cAMP) accumulation in the C6BU-1 cells transfected with 5-HT1A receptor gene. Further, this 8-OH-DPAT-induced inhibition of forskolin-stimulated activity was significantly attenuated after pre-exposure to 5-HT (10 microM) for 12 h. Spiperone (10 microM), a 5-HT1A and 5-HT2A antagonist, prevented 5-HT-induced desensitization of 5-HT1A receptor, but a selective 5-HT2A receptor antagonist, ketanserin, did not. In addition, pre-exposure to a selective 5-HT2A agonist, 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI, 10 microM), for 24 h did not alter the inhibitory effect of 8-OH-DPAT on forskolin-stimulated cAMP accumulation in these transfected cells, suggesting that prolonged exposure to 5-HT induced 5-HT1A receptor desensitization, mediated by 5-HT1A receptor but not 5-HT2A receptors.

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.

Biochemical and behaviour changes induced by acute stress in a chronic variate stress model of depression: the effect of amitriptyline

This paper examines the biochemical and behaviour changes induced by an acute stress (five 10-s, 1-mA foot-shocks) in three groups of rats: (1) never stressed, (2) subjected to chronic variate stress for 20 days, (3) subjected to the same chronic stress and treated with 5 mg/kg per day amitriptyline. After 15 min, acute stress led to a marked reduction in cortical beta-adrenoceptor and 5-HT2 receptor density, whereas the density of the 5-HT1A receptors was unchanged. Chronic stress also increased beta-adrenoceptor and 5-HT2 receptor density and had no effect on 5-HT1A. Acute stress diminished the density of beta-adrenoceptors in chronically stressed animals, but did not alter that of the two 5-HT populations. Amitriptyline alone reduced beta-adrenoceptor and 5-HT2 receptor densities only. Acute stress applied to animals treated with amitriptyline reduced 5-HT1A receptors, and caused a further beta-adrenoceptor decrease, but had no further effect on the 5-HT2 receptors. On behaviour, chronic stress diminished reactivity to the acute stress. This reduction was fully abolished by amitriptyline. An open-field study showed that acute stress reduced motor activity, increased latency times and diminished rearing in the controls, whereas chronic stress reduced motor activity only. No significant changes in behaviour were induced by the acute stress in animals subjected to chronic stress. The combination of chronic stress with amitriptyline was accompanied by a diminution of exploratory activity that persisted after the acute stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased density of mu-opioid receptors in the postmortem brain of suicide victims

The biochemical status of mu-opioid receptors in suicide was evaluated by [3H]DAGO specific binding in postmortem human brains from 15 suicide victims and 15 controls. The density (Bmax) in frontal cortex and thalamus was directly correlated with age. In the frontal cortex and caudate but not in the thalamus of suicide victims the density of mu-opioid receptors was 36-39% higher than in controls. KD values in suicide victims were similar to those in control group (range 1.4-2.2 nM). The results suggest an increase of mu-opioid receptors in suicide associated to some brain areas showing the mu2-opioid receptor subtype.

Beta-adrenergic receptor subtypes in stress-induced behavioral depression

The purpose of this study was to examine the role of beta-adrenergic receptors in an animal model of stress-induced behavioral depression. beta-Adrenergic receptors in several brain regions and leukocytes of rats were determined by receptor binding techniques using 125I-cyanopindolol (cyp) as ligand and propranolol as displacer for total beta-adrenergic receptors, and ICI 86,406 for beta 1- and ICI 118,551 for beta 2-adrenergic receptors. We observed that the maximum number of binding sites (Bmax) and the apparent dissociation constant (Kd) of 125I-cyp binding to total beta-adrenergic receptors were increased in hippocampus of stressed rats with escape deficits (48 h after training) as compared to control rats. This increase was due to an increase in Bmax and Kd of 125I-cyp binding to beta 1-adrenergic receptors but not to beta 2-adrenergic receptors. There was no significant difference in beta 1-adrenergic receptors in cortex and cerebellum or beta 2-adrenergic receptors in hippocampus, cortex, cerebellum, or leukocytes of stressed (48 h after training) rats with escape deficits as compared to control rats. Interestingly, it was observed that beta 1- and beta 2-adrenergic receptors in various brain regions (cortex, cerebellum, and hippocampus) and beta 2-adrenergic receptors in leukocytes of stressed rats (10 days after training) were not significantly different from control rats, although escape deficits were still present. These results suggest that abnormalities in adrenergic neurotransmission are associated with an upregulation of beta 1-adrenergic receptors, which in turn may be involved in the early stages of behavioral deficits caused by uncontrollable shock.

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.

Effects of serotonin precursors on the negative feedback effects of glucocorticoids on hypothalamic-pituitary-adrenal axis function in depression

In order to investigate the relationships between brain serotonergic turnover and hypothalamic-pituitary-adrenal (HPA) axis function in unipolar depression, the authors measured intact adrenocorticotropic hormone (ACTH) and cortisol levels in baseline conditions and after combined dexamethasone (1 mg PO) and L-5-hydroxytryptophan (L-5-HTP, 200 mg PO) administration in 13 minor, 17 simple major, and 17 melancholic subjects. L-5-HTP significantly enhanced post-DST ACTH and cortisol secretion in major--but not in minor--depressed subjects. Major depressed subjects with or without melancholia exhibited significantly higher post-DST ACTH and cortisol responses to L-5-HTP than minor depressed subjects. L-5-HTP administration converted some major depressed ACTH or cortisol suppressors into nonsuppressors. L-5-HTP stimulated ACTH or cortisol secretion to the same extent in major depressed HPA-axis suppressors and nonsuppressors. It is concluded that L-5-HTP loading may augment ACTH and, consequently, cortisol escape from suppression by dexamethasone in major but not in minor depressed subjects. The findings show that serotonergic mechanisms modulate the negative feedback of glucocorticoids on central HPA-axis regulation. It is hypothesized that the higher L-5-HTP-induced post-DST HPA-axis hormone responses in major depression reflect upregulated 5-HT2 receptor-driven breakthrough secretion of pituitary ACTH from suppression by dexamethasone.

Reversal by imipramine of beta-adrenoceptor up-regulation induced in a chronic mild stress model of depression

Male Wistar rats were subjected to a chronic mild stress procedure involving different stress stimuli applied for 8 weeks. During this time the consumption of 1% sucrose solution was monitored at weekly intervals. After the first 3 weeks, when stressed animals displayed a reduction of sucrose consumption, the control and stressed groups were divided into subgroups receiving daily placebo or imipramine (10 mg/kg/day) treatment. After 5 weeks of treatment, 24 h after the last injection, the rats were killed and beta-adrenoceptor density and affinity in cortical membrane preparations and the accumulation of cyclic AMP in cortical slices stimulated with noradrenaline were assessed. While in stressed placebo-treated rats the sucrose consumption remained reduced, in the imipramine-treated group the level of consumption gradually returned to control values. The stressed placebo-treated rats also displayed an increase in cortical beta-adrenoceptor density (by 34%) with no changes in affinity, and an increase (22%) in the cyclic AMP response to noradrenaline in cortical slices. Imipramine, which in non-stressed rats did not affect sucrose intake but depressed the beta-adrenoceptor density and the cyclic AMP response, reversed the stress-induced decrease in sucrose consumption and the increase in the beta-adrenoceptor density; at physiological noradrenaline concentrations it also reduced the enhanced cyclic AMP response. The results suggest that the chronic mild stress procedure produces behavioral and biochemical changes consistent with a realistic model of depression in animals.

5-Hydroxytryptamine2 and beta-adrenergic receptor regulation in rat brain following chronic treatment with desipramine and fluoxetine alone and in combination

A chronic (14-day) study was initiated to investigate the effects of combined fluoxetine (FLU) and desipramine (DMI) treatment on the densities and affinities of beta-adrenergic and 5-hydroxytryptamine2 (5-HT2) receptors. Male Sprague-Dawley rats were administered the following doses using osmotic minipumps: FLU, 10 mg/kg/day; DMI, 5, 10, or 15 mg/kg/day; FLU, 10 mg/kg/day, plus DMI, 5 mg/kg/day; or vehicle (distilled water). After 14 days the cortex was dissected out and used for [3H]-ketanserin (5-HT2) binding, [3H]CGP-12177 (beta-adrenergic) binding, and drug level analysis. All animals receiving DMI showed significant down-regulation of 5-HT2 receptors except those receiving FLU in combination. DMI down-regulated beta-adrenergic receptors in a dose-dependent manner, with significantly greater down-regulation seen with the combination than with DMI (5 mg/kg/day) alone. This latter effect was apparently the result of greater levels of DMI in cortex with the combination than with DMI (5 mg/kg/day) alone. FLU had no effect on 5-HT2 or beta-adrenergic receptors on its own. Coadministration of FLU and DMI resulted in a doubling of levels of FLU and its demethylated metabolite, norfluoxetine (NFLU), and a tripling of DMI levels compared with values observed when FLU (10 mg/kg/day) or DMI (5 mg/kg/day) was administered alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain 5-HT2 receptors in suicide victims: violence of death, depression and effects of antidepressant treatment

5-HT2 binding sites were quantitated, by saturation binding with [3H]ketanserin, in six brain regions from 73 subjects who died by suicide and 70 sudden death controls. There were no significant differences in the number of 5-HT2 binding sites between suicides and controls in any brain region within the total suicide group or when suicides were divided on the basis of violence of death. Similar results were found when suicides were divided into those with a firm retrospective diagnosis of depression, whether they had been receiving antidepressants or not, and those who were heterogeneous in respect of psychiatric diagnosis and drug treatment. The present findings contrast with previous reports of higher cortical 5-HT2 binding sites in suicides; possible reasons for these differences are discussed.

Brain 5-HT1A, 5-HT1D, and 5-HT2 receptors in suicide victims

We report on 5-HT1A, 5-HT1D, and 5-HT2 binding sites in 23 control subjects and 18 suicide victims subdivided according to the method of death and the previous existence of depressive symptoms. No difference in maximum binding (Bmax) or binding affinity (Kd) was found between the control and overall suicide groups for the binding sites studied. The drug overdose subgroup showed, however, a significant decrease in the 5-HT1A binding affinity, probably explained by the higher sensitivity of this binding site to the acute administration of tricyclic antidepressants. A significant decrease in 5-HT1D binding affinity was also found in the depressed suicides, together with a significant decrease in the number of 5-HT1D binding sites in the nondepressed suicides. Further studies should be carried out on the 5-HT1D binding site as it might represent a new tool in the understanding of the depressive illness.

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.

Effects of imipramine on serotonergic and beta-adrenergic receptor binding in a realistic animal model of depression

Chronic exposure to mild unpredictable stress (CMS) has previously been found to cause an antidepressant-reversible decrease in the consumption of palatable sweet solutions. In the present study, in addition to confirming these behavioural observations, the binding properties of cortical beta-adrenergic and 5HT2 receptors, and hippocampal 5HT1A receptors were studied (using the ligands [3H]-dihydroalprenolol, [3H]-ketanserin and [3H]-8-OH-DPAT, respectively), following 7 weeks of CMS and 4 weeks of imipramine treatment (10 mg/kg per day). CMS increased Bmax for all three receptor systems. Imipramine decreased Bmax, reversing the effect of CMS, for beta-adrenergic and 5HT2 receptor binding, but increased Bmax for 5HT1A receptor binding. KDs were unaffected by either treatment. The beta-receptor and 5HT2 receptor binding data are consistent with accounts of antidepressant action derived from studies in normal animals, but the 5HT1A receptor binding data are more difficult to reconcile. In no case was there a good correlation between receptor binding and behavioural data.

Gender differences in completed and attempted suicides

Attempted suicides occur primarily among women, while completed suicides occur primarily among men. Risk factors for both attempted and completed suicides include mental and addictive disorders, disrupted family environments, and precipitating events. This article presents an overview of findings on gender differences from epidemiologic studies of completed and attempted suicides, with a focus on suicide attempts among women, and discusses possible reasons for gender differences in suicidal behaviors.

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.

Electroconvulsive shock decreases excitatory responses to serotonin in the caudate nucleus of the rat

1. The present study explored the changes on the firing rate of caudate neurons, and the response to serotonin locally applied in rats submitted to electroconvulsive shock. 2. Electroconvulsive shock diminished the firing rate of caudate neurons and blocked the excitatory response produced by serotonin in a small amount of serotonin-sensitive neurons. 3. Results are likely to be related with transient changes in the receptor's affinity and dissociation constants, which may impinge on immediate memory retrieval.

Dietary amino acids and brain function

Two groups of amino acids--the aromatic and the acidic amino acids--are reputed to influence brain function when their ingestion in food changes the levels of these amino acids in the brain. The aromatic amino acids (tryptophan, tyrosine, phenylalanine) are the biosynthetic precursors for the neurotransmitters serotonin, dopamine, and norepinephrine. Single meals, depending on their protein content, can rapidly influence uptake of aromatic amino acid into the brain and, as a result, directly modify their conversion to neurotransmitters. Such alterations in the production of transmitters can directly modify their release from neurons and, thus, influence brain function. The acidic amino acids glutamate and aspartate are themselves brain neurotransmitters. However, they do not have ready access to the brain from the circulation or the diet. As a result, the ingestion of proteins, which are naturally rich in aspartate and glutamate, has no effect on the level of acidic amino acid in the brain (or, thus, on brain function by this mechanism). Nevertheless, the food additives monosodium glutamate and aspartame (which contains aspartate) have been reputed to raise the level of acidic amino acid in the brain (when ingested in enormous amounts), to modify brain function, and even to cause neuronal damage. Despite such claims, a substantial body of published evidence clearly indicates that the brain is not affected by ingestion of aspartame and is affected by glutamate only when the amino acid is administered alone in extremely large doses. Therefore, when consumed in the diet neither compound presents a risk to normal brain function.

Serotonin-induced platelet intracellular calcium mobilization in depressed patients

Serotonin(5-HT)-stimulated intracellular calcium(Ca) mobilization was measured in the platelets of depressed patients to assess 5-HT2 receptor function. The 5-HT-induced Ca response was significantly higher in unmedicated patients with bipolar depression and melancholic major depression than in those with non-melancholic major depression and normal controls. The enhanced Ca response to 5-HT failed to correlate with severity of depressive symptoms. In patients with bipolar disorder and melancholic major depression, there was no significant difference in 5-HT-stimulated Ca response between the unmedicated group and those in remission. These results suggest that 5-HT2 receptor function is increased in some types of depression, and raise the possibility that the enhanced Ca response to 5-HT may be trait dependent rather than state dependent.