Serotonin 5-HT2 receptor binding on blood platelets--a peripheral marker for depression?

Is there a relationship between morphological and functional platelet changes and depressive disorder?

BACKGROUND

Blood platelets, due to shared biochemical and functional properties with presynaptic serotonergic neurons, constituted, over the years, an attractive peripheral biomarker of neuronal activity. Therefore, the literature strongly focused on the investigation of eventual structural and functional platelet abnormalities in neuropsychiatric disorders, particularly in depressive disorder. Given their impact in biological psychiatry, the goal of the present paper was to review and critically analyze studies exploring platelet activity, functionality, and morpho-structure in subjects with depressive disorder.

METHODS

According to the PRISMA guidelines, we performed a systematic review through the PubMed database up to March 2020 with the search terms: (1) platelets in depression [Title/Abstract]"; (2) "(platelets[Title]) AND depressive disorder[Title/Abstract]"; (3) "(Platelet[Title]) AND major depressive disorder[Title]"; (4) (platelets[Title]) AND depressed[Title]"; (5) (platelets[Title]) AND depressive episode[Title]"; (6) (platelets[Title]) AND major depression[Title]"; (7) platelet activation in depression[All fields]"; and (8) platelet reactivity in depression[All fields]."

RESULTS

After a detailed screening analysis and the application of specific selection criteria, we included in our review a total of 106 for qualitative synthesis. The studies were classified into various subparagraphs according to platelet characteristics analyzed: serotonergic system (5-HT2A receptors, SERT activity, and 5-HT content), adrenergic system, MAO activity, biomarkers of activation, responsivity, morphological changes, and other molecular pathways.

CONCLUSIONS

Despite the large amount of the literature examined, nonunivocal and, occasionally, conflicting results emerged. However, the findings on structural and metabolic alterations, modifications in the expression of specific proteins, changes in the aggregability, or in the responsivity to different pro-activating stimuli, may be suggestive of potential platelet dysfunctions in depressed subjects, which would result in a kind of hyperreactive state. This condition could potentially lead to an increased cardiovascular risk. In line with this hypothesis, we speculated that antidepressant treatments would seem to reduce this hyperreactivity while representing a potential tool for reducing cardiovascular risk in depressed patients and, maybe, in other neuropsychiatric conditions. However, the problem of the specificity of platelet biomarkers is still at issue and would deserve to be deepened in future studies.

Platelet serotonin-binding and dexamethasone suppression test in melancholia and dysthymia

Platelet serotonin-binding (Bmax), using tritiated-seroionin as the ligand, was determined in 75 patients suffering from major depression with melancholia and in 26 patients diagnosed from dysthymic disorder. Twenty-five normal subjects were used as a control group. The melancholic group had significantly lower Bmaxvalues (mean: 6.7 ± 6.1 pmol/108platelets) than either dysthymic (9.3 ± 3.9 pmol/108platelets) or control (9.2 ± 4.8 pmol/108platelets) groups, while there were no significant differences between the two latter groups. There was also a significant difference on postdexamethasone Cortisol between melancholic (6.3 ± 7.1μg/dL) and dysthymic (1.4 ± 1.4μg/dL) groups, with a higher rate of nonsuppressors in melancholic groups. Although both tests were abnormal in the melancholic group, no relationship was found between platelet serotonin-binding and the dexaniethasone suppression test.

Sound mind vs sound heart

Depressive and anxiety disorders have both have been associated with an increased risk of cardiovascular disease. This article highlights the multifactorial and bidirectional interaction between cardiovascular diseases, depression and anxiety, and the need for early assessment, diagnosis and intervention.

Genes in the serotonin pathway are associated with bipolar affective disorder in a Han Chinese population

Serotonin plays an important role in mood regulation, but the involvement of serotonin pathway genes in the development of bipolar I disorder (BP-I), a mood disorder, is not clear. We selected 21 single-nucleotide polymorphisms (SNPs) within the HTR2A gene, 8 within the SLC6A4 gene and 23 within the TPH2 gene for genotyping using the GoldenGate genotyping assay. A total of 375 patients with BP-I and 475 normal controls were recruited. Two out of 21 SNPs (rs1475196 and rs9567747) in the HTR2A gene and 1/23 SNPs (rs17110566) in the TPH2 gene were significantly associated with BP-I, both genotype-wise and allele-wise. Furthermore, a specific haplotype in the HTR2A gene showed a significant association with BP-I. Our results indicate that the HTR2A and TPH2 genes in the serotonin pathway play important roles in susceptibility to BP-I.

Biological basis of suicide and suicidal behavior

OBJECTIVE

Suicide is a major public health concern as each year 30000 people die by suicide in the USA alone. In the teenage population, it is the second leading cause of death. There have been extensive studies of psychosocial factors associated with suicide and suicidal behavior. However, very little is known about the neurobiology of suicide. Recent research has provided some understanding of the neurobiology of suicide, which is the topic of this review.

METHODS

Neurobiology of suicide has been studied using peripheral tissues such as platelets, lymphocytes, and cerebrospinal fluid obtained from suicidal patients or from the postmortem brains of suicide victims.

RESULTS

These studies have provided encouraging information with regard to the neurobiology of suicide. They show an abnormality of the serotonergic mechanism, such as increased serotonin receptor subtypes and decreased serotonin metabolites (e.g. 5-hydroxyindoleacetic acid). These studies also suggest abnormalities of receptor-linked signaling mechanisms such as phosphoinositide and adenylyl cyclase. Other biological systems that appear to be dysregulated in suicide involve the hypothalamic-pituitary-adrenal axis, and neurotrophins and neurotrophin receptors. More recently, several studies have also indicated abnormalities of neuroimmune functions in suicide.

CONCLUSIONS

Some encouraging information emerged from the present review, primarily related to some of the neurobiological mechanisms mentioned above. It is hoped that neurobiological studies may eventually result in the identification of appropriate biomarkers for suicidal behavior as well as appropriate therapeutic targets for its treatment.

Glucocorticoid treatment increases density of serotonin 5-HT2A receptors in humans

BACKGROUND

Interactions between the serotonergic system and the hypothalamic-pituitary-adrenal axis have been suggested, albeit the details for such interactions have yet to be established. Animal studies have shown that the density of serotonin 5-HT2A receptors is increased after administration of exogenous glucocorticoids.

OBJECTIVE

The objective of this study was to explore possible changes in the pattern of density and affinity of 5-HT2A receptors in humans after treatment with glucocorticoids.

METHODS

Using a radioactive binding assay, the density and affinity (measured as Bmax and Kd) of 5-HT2A serotonin receptors were measured in blood samples drawn from 27 individuals diagnosed with polymyalgia rheumatica and/or giant cell arteritis before and after start of an oral treatment with prednisolone. For each patient Bmax and Kd at baseline before prednisolone treatment were compared with Bmax and Kd in samples drawn at a first and second follow-up clinic visit at an average of 8.8 (±2.5) days and 33.6 (±6.8) days, respectively.

RESULTS

The density of 5-HT2A receptors increased after treatment in 23 individuals. The mean Bmax value at baseline for all patients was 45.2 fmol/mg protein compared with 64.9 fmol/mg protein in the corresponding samples drawn at the second follow-up visit (p=0.001). There also was an association between individuals accumulated prednisolone dose and the magnitude of change in Bmax between baseline and the first follow-up visit. Erythrocyte sedimentation rate, platelet count or gender had no influence on the results. There were no significant differences in Kd during the treatment period. However, a low Kd value at baseline was a predictor for an increase in Bmax following treatment.

CONCLUSIONS

The results of this study showed that the density of 5-HT2A serotonin receptors in man is increased after a subchronic treatment with glucocorticoids. The magnitude of the increase appears to be associated with the affinity of 5-HT2A receptors before treatment and the accumulated dose of glucocorticoid early in the treatment period.

Clinical and serotonergic predictors of non-affective acute remitting psychosis in patients with a first-episode psychosis

OBJECTIVE

The study aimed to establish clinical predictors of non-affective acute remitting psychosis (NARP) and assess whether these patients showed a distinct serotonergic profile.

METHOD

First-episode never treated psychotic patients diagnosed of paranoid schizophrenia (n=35; 21 men and 14 women) or NARP (n=28; 15 men and 13 women) were included.

RESULTS

NARP patients showed significantly lower negative symptomatology, better premorbid adjustment, shorter duration of untreated psychosis, more depressive symptomatology and a lower number of 5-HT2A receptors than the paranoid schizophrenia patients. In the logistic regression, the four variables associated with the presence of NARP were: low number of 5-HT2A receptors; good premorbid adjustment; low score in the item 'hallucinatory behaviour' and reduced duration of untreated psychosis.

CONCLUSION

Our findings support the view that NARP is a highly distinctive condition different from either affective psychosis or other non-affective psychosis such as schizophrenia, and highlight the need for its validation.

Effect of selective serotonin reuptake inhibitors on platelet activation: can they prevent acute myocardial infarction?

In recent years a large body of evidence from several longitudinal studies has emerged suggesting that depression is an independent risk factor for cardiovascular disease (CVD) and that the association between depression and increased CVD risk is not merely due to negative mood-driven behavior related with depression. Even though the underlying mechanisms are not well understood, several hypotheses and explanations have been proposed such as increased activation of the hypothalamic-pituitary-adrenal axis, abnormalities in the sympathoadrenal system, or abnormalities in platelet function. Platelet function abnormalities, including increased platelet reactivity, may predispose patients with depressive disorders to clotting diatheses and may explain their vulnerability to CVD. Serotonin secreted by platelets induces both platelet aggregation and coronary vasoconstriction. Even though serotonin itself is only a weak platelet agonist, it markedly enhances platelet reactions to a variety of other agonists. Several studies have shown that selective serotonin reuptake inhibitors (SSRIs) reduce platelet and whole blood serotonin concentrations after repeated doses, and could therefore exert an inhibitory effect on platelet activation. For that reason, it was hypothesized that SSRIs could have a protective effect against myocardial infarction (MI). Results from three currently available epidemiological studies assessing the risk of MI in patients treated with antidepressants, including SSRIs, are controversial with respect to a potential beneficial effect of SSRIs on CVD risk in depressed patients. However, there is evidence that exposure to SSRIs does not substantially increase the risk of CVD in patients. A recent randomized, double-blind, placebo-controlled, multicenter trial that evaluated the safety and efficacy of the SSRI sertraline in patients with major depression and acute MI or unstable angina suggested that sertraline is well tolerated and effective. Further epidemiological studies or longer-term clinical trials may shed more light on this issue, and answer the question conclusively, whether the effect of SSRIs on platelets or another mechanism translates into a decreased risk of CVD in depressed patients.

The metabolism of serotonin in neuronal cells in culture and platelets

The aim of this study is to find a relationship between serotonin (5-HT) and its metabolite 5-hydroxy indol acetic acid (5-HIAA) in hippocampus, frontal neocortex and platelets. Serotonin and 5-HIAA were measured in cultured neurons and compared with those produced by human platelets. The cortical neuronal 5-HIAA/serotonin ratio was 4.7 and for hippocampal neurons it was 3.2. In human platelets, this ratio was 1.35 suggesting that the highest serotonin metabolism occurs in the frontal neocortex followed by the hippocampus and platelets. In the presence of 0.3 microM of p-chlorophenylalanine both cultured neurons and platelets exhibited an approximately 50% decrease in serotonin and 5-HIAA concentration suggesting similarities in the metabolic profile in both preparations. In addition, we found that serotonin by itself does not play any role in platelet aggregation but potentiates this phenomenon in the presence of calcium ionophore A23187. This synergistic interaction between serotonin (2-5 microM) and A23187 (0.5-2 microM) was inhibited by serotonin receptor blockers [methysergide (IC50 = 18 microM) and cyproheptadine (IC50, 20 microM)] and calcium channel blockers (verapamil and diltiazem, IC50 = 20 and 40 microM, respectively) that indicate both mechanisms are receptor mediated. Similarly, U73122, an inhibitor of phospholipase C (PLC), blocked the synergistic effect of serotonin and ionophore at an IC50 value of 9.2 microM. Wortmannin, a phosphoinositide 3-kinase (PI 3-K) inhibitor, also blocked the response (IC50 = 2.6 microM) by inhibiting respiratory burst. However, neither genistein, a tyrosine-specific protein kinase inhibitor, nor chelerythrine, a protein kinase C (PKC) inhibitor, affected aggregation. Our results are strongly suggestive of a synergistic interaction between serotonin type-2 and Ca-ionophore via a PLC/Ca signalling pathway.

Future prospects in depression research

Major depression is a common, disabling, and often difficult-to-treat illness. Decades of research into the neurobiology and treatment of depression have greatly advanced our ability to manage this disorder. However, a number of challenges remain. A substantial number of depressed patients do not achieve full remission despite optimized treatment. For patients who do achieve resolution of symptoms, depression remains a highly recurrent illness, and repeated episodes are common. Finally, little is known about how depression might be prevented, especially in individuals at increased risk. In the face of these challenges, a number of exciting research efforts are currently under way and promise to greatly expand our knowledge of the etiology, pathophysiology, and treatment of depression. This review highlights these future prospects for depression research with a specific focus on lines of investigation likely to generate novel, more effective treatment options.

Platelet inhibition beyond conventional antiplatelet agents: expanding role of angiotensin receptor blockers, statins and selective serotonin reuptake inhibitors

Aspirin, dipyridamole, cilostazol, thienopyridines and glycoprotein IIb/IIIa inhibitors represent the classical examples of the established antiplatelet agents commonly used for the secondary prevention in patients after vascular events. Obviously, the era of expanding antiplatelet regimens and indications may require new agents as the substitutes, or additions to the available strategies. However, recent results of the majority of antiplatelet trials strongly suggest boarder line advantages in clinical outcomes, and higher associated bleeding risks with the novel antiplatelet agents or/and regimens. Moreover, unexpected failures, such as lack of efficacy of clopidogrel and aspirin combination for ischaemic stroke prevention (MATCH), or use of the same antiplatelet regimen for the primary vascular prevention (CHARISMA) raise legitimate concerns that the concept 'the more the better' may not be valid. Broad use of statins, angiotensin receptor blockers and selective serotonin reuptake inhibitors may be in part responsible for the lack of impressive results with the antiplatelet therapy because each of these drug classes per se inhibits platelets. In this review, we discuss the available evidence and potential clinical significance of these findings.

Escitalopram, but not its major metabolites, exhibits antiplatelet activity in humans

BACKGROUND

Clinical depression has been identified as an independent risk factor for increased mortality during follow-up in patients suffered from acute coronary events, whereas increased platelet activity has been proposed as one of the mechanisms for this association. Some evidence suggests that selective serotonin reuptake inhibitors and/or their metabolites exhibit potent antiplatelet properties.

METHODS

We assessed the in vitro effects of preincubation with escalating (50-200 nmol/L) concentrations of escitalopram (ESC) S-desmethyl-citalopram (S-DCT), and S-di-desmethyl-citalopram, (S-DCT) on platelet aggregation through the expression of major surface receptors using flow cytometry and quantitatively using platelet function analyzers in 20 healthy volunteers.

RESULTS

Pretreatment of blood samples with ESC with ESC resulted in a significant inhibition of platelet aggregation induced by ADP (P = 0.0001) and by collagen with the highest dose (P = 0.001). Surface platelet expressions of glycoprotein Ib (CD42) (P = 0.04), lysosome associated membrane protein-3 (CD63) (P = 0.02), and GP37 (CD165) (P = 0.03) was decreased in the ESC-pretreated samples. Closure time by the Platelet Function Analyzer-100 analyzer was prolonged for the 200 nmol/L dose (P = 0.02), indicating platelet inhibition under high shear conditions. Two major metabolites of ESC, namely S-DCT and S-DDCT, did not affect platelet activity.

CONCLUSION

Escitalopram, but not its metabolites, exhibited selective inhibition of human platelet properties. The direct antiplatelet effect of ESC requires further prospective or ex vivo testing to determine the possible clinical advantage of this finding.

Common genetic vulnerability to depressive symptoms and coronary artery disease: a review and development of candidate genes related to inflammation and serotonin

OBJECTIVE

Although it is well established that depressive symptoms are associated with recurrent cardiac events among cardiac patients and novel cardiac events among participants with no known coronary artery disease (CAD), the nature of this association remains unclear. In this regard, little attention has been paid to the possibility that common genetic vulnerability contributes to both depressive symptoms and CAD. In this paper, we review the existing evidence for common genetic contributions to depression and CAD, primarily using evidence from twin and family studies, followed by a review of two major pathophysiological mechanisms thought to underlie covariation between depressive symptoms and CAD: inflammation and serotonin. We conclude with an overview of select candidate genes within these pathways.

METHODS

Literature review.

RESULTS

In twin studies, both depression and CAD appear heritable. In the only twin study to consider depression and CAD jointly, the correlation across heritabilities was 0.42, suggesting that nearly 20% of variability in depressive symptoms and CAD was attributable to common genetic factors. In addition, although it is plausible that genetic variation related to inflammation and serotonin may be associated with both depression and CAD, genetic variation related to inflammation has been primary examined in relation to CAD, whereas genetic variation in the serotonin system has been primarily examined in relation to depression.

CONCLUSIONS

It appears that the covariation of depressive symptoms and CAD may be attributable, in part, to a common genetic vulnerability. Although several pathways may be involved, genes within the inflammation and serotonin pathways may serve as good candidates for the first steps in identifying genetic variation important for depression, CAD or both.

Heart and mind: (1) relationship between cardiovascular and psychiatric conditions

The relationship of our emotions and psyche to heart disease is intriguing. In this article we have reviewed the evidence linking cardiovascular and neuropsychiatric disorders and the possible mechanisms and pathophysiology of this association. This review is derived from Medline searches (1966-2002) using the relevant search terms (psychiatric disease, cardiovascular disease, depression, anxiety, and pathophysiology). Finally, the possible role of using mood enhancing therapies (mainly antidepressants) and their safety in patients with cardiovascular disorders is briefly discussed. In a companion paper, the therapeutic aspects of these two conditions is highlighted.

Single and repeated stress-induced modulation of phospholipase C catalytic activity and expression: role in LH behavior

PI-PLC, a critical enzyme of the phosphoinositide (PI) signaling pathway, mediates many physiological functions in the brain, including cellular plasticity. Stress-induced learned helplessness (LH) in animals serves as a model of behavioral depression. Recently, we observed that repeated stress prolongs the duration of LH behavior in rats, enabling us to compare neurobiologic abnormalities in acute and chronic depression. Here we examine whether LH behavior is associated with alterations in phospholipase C (PLC), and whether repetition of inescapable shock has similar or dissimilar effects on PLC to those of the single-stress paradigm. Rats were exposed to inescapable shock either once on day 1, or twice, on days 1 and 7. Rats were tested for escape latency on days 2 and 4 after day 1 inescapable shock or on days 2, 8, and 14 after day 1 and 7 inescapable shock. PI-PLC activity and mRNA and protein expression of three different PLC isozymes were determined in the frontal cortex and hippocampus. Higher escape latencies were observed in LH rats tested on day 2 after single inescapable shock and on day 14 after repeated inescapable shock. Single inescapable shock reduced PI-PLC activity in the frontal cortex and hippocampus of LH rats. On the other hand, repeated inescapable shock not only reduced PI-PLC activity in these brain areas of LH rats but also selectively decreased the expression of PLC beta1 and PLC gamma1 isozymes. Our results suggest different responsiveness at the level of PI-PLC after single vs repeated stress, and that reductions in PLC may be critical in the pathophysiology of depression and other stress-related disorders.

Venous thromboembolism and escitalopram

Selective serotonin reuptake inhibitors (SSRIs) are currently used as a first-line treatment for depression, as they have a favorable side-effect profile. Escitalopram, a new SSRI, is also well-tolerated and serious side effects are rarely associated with its use. There have been several reports that SSRIs might increase bleeding tendency in some patients by affecting platelet function. However, to our knowledge, there have been no reports about their relation to thrombosis. In this brief report, we present a case of venous thromboembolism associated with escitalopram in a patient with psychotic depression without any major risk factors for thrombosis. SSRIs might have a dual effect on platelet function. The immediate and early effect of SSRI use on platelets might be an increase be an in tendency for thrombosis, whereas the late effect after repeated dosing might be an increase in tendency to bleed, as suggested by previous literature.

Influence of menstrual cycle on platelet serotonin uptake site and serotonin2A receptor binding

Depression and anxiety are common health problems affecting women, particularly during the reproductive years. Major depression is two to three times as common in women than in men. Neuroendocrine factors are likely to contribute to this overall increased risk for developing mood disorders in women, and the neuroendocrine influence is most obviously seen in women with premenstrual dysphoric disorder (PMDD) as these women experience depressed mood and anxiety premenstrually only during ovulatory cycles. Moreover, dysfunction of serotonergic transmission has been regarded as an important mechanism in several psychiatric disorders and ovarian steroids have been shown to profoundly influence the activity of the serotonergic system. Given these facts, the purpose of this study was to examine whether binding of [3H]paroxetine to the platelet serotonin transporter or binding of [3H]lysergic acid diethylamide ([3H]LSD) to the platelet 5-HT2A receptor are influenced by the cyclical changes in circulating estradiol and progesterone that occur during the menstrual cycle. We examined 28 healthy women, without oral contraceptives and with regular menstrual cycles. In the late follicular phase, Bmax for [3H]paroxetine binding was significantly higher than in the ovulatory (p<0.01), early luteal phase (p<0.05) and mid-luteal phase (p<0.01). Bmax for [3H]LSD binding was significantly higher in the early follicular phase and the early luteal phase compared to the mid-luteal phase (p<0.001 and p<0.05, respectively). In the early follicular phase and the ovulatory phase, significant correlations between estradiol serum concentrations and Kd for [3H]paroxetine were obtained (p<0.001, respectively). In the luteal phase, significant inverse correlations between progesterone as well as estradiol serum concentrations and Kd for [3H]LSD binding were found (p<0.05, respectively).

Serotonergic platelet markers of suicidal behavior--do they really exist?

BACKGROUND

Abnormal changes in platelets used as peripheral markers of central serotonergic functions are said to be associated with suicidality and depression, but this association has not been supported by consistent findings.

AIM

This review based on selected, often quoted publications in this area focuses firstly, on obviously contradictory findings and, secondly, on potential methodological flaws explaining these discrepancies.

RESULTS

The platelet 5-HT transporter has been found to have an inconsistent association with suicidality; furthermore, the specificity of imipramine for the 5-HT transporter is most likely low, since the number of platelet impramine binding sites has not been reliably associated with platelet serotonin uptake (Vmax). Significant changes of platelet serotonin content in suicidal individuals, as described in various studies, are most likely due to washout periods that are too short to eliminate the effects of a previous drug intake, or, in violent suicide attempters, due to blood loss and dilution. Similar methodological shortcomings might account for an often-reported elevated number of platelet 5-HT(2) receptor binding sites in suicidal individuals. In many studies, the results have not been sufficiently controlled for drug effects on platelet 5-HT(2) receptors, and associations of platelet 5-HT(2) binding with selective classifications of suicidal behavior are often generalized as further evidence for an association of platelet 5-HT(2) receptors with 'suicidality'. Finally, changes in platelet MAO-B-activity in suicidal patients have not been reproducibly found, and the impact of smoking on MAO-B activity has not been controlled in any studies.

CONCLUSIONS

Methodological flaws such as small sample sizes, insufficient matching criteria for controls, use of inadequate ligands in binding experiments, nonconsideration of comorbidity etc. and considerable methodological differences between studies limit their validity and comparability. It does not seem possible, at present, to integrate published findings and concepts into a plausible biological model of suicidality.

Enhanced platelet/endothelial activation in depressed patients with acute coronary syndromes: evidence from recent clinical trials

Platelets play a key role in the progression of acute coronary syndromes (ACS). Clinical depression alone is also associated with enhanced platelet activation. The purpose of this study was to compare concentrations of established biomarkers of enhanced platelet/endothelial activation in clinically depressed versus non-depressed patients enrolled in recent clinical trials for ACS. Two hundred and eighty-one baseline plasma samples from patients with acute myocardial infarction (ASSENT-2; n = 41), with ACS (PRONTO; n = 126) and with clinical depression plus previous acute coronary syndrome within 6 months (SADHART; n = 64), and from normal healthy controls (n = 50) were analyzed. Blood was drawn before applying any therapeutic strategies including interventions, thrombolytics, infusions, and selective serotonin re-uptake inhibitors. Platelet factor 4, beta-thromboglobulin, platelet/endothelial cell adhesion molecule-1, P-selectin, thromboxane, prostacyclin, vascular cell adhesion molecule-1, and E-selectin were measured by enzyme-linked immunosorbent assay by a single core laboratory. Patients with ACS exhibited a higher degree of platelet activation than controls independently of the presence of depression. Plasma levels of P-selectin, thromboxane, prostacyclin, and vascular cell adhesion molecule-1 were the highest in the acute myocardial infarction group when compared with ACS despite the presence or absence of clinical depression. Surprisingly, patients with ACS and depression exhibited the highest levels of platelet factor 4, beta-thromboglobulin, and platelet/endothelial cell adhesion molecule-1 when compared with myocardial infarction or angina patients without clinical depression. E-selectin plasma level was constantly elevated compared with controls but did not differ among the groups dependent on the incidence of depression. The depressed plus ACS group had higher plasma levels of all biomarkers compared with the non-depressed patients. Retrospective analysis of the data from several clinical trials reveals that clinical depression is associated with enhanced activation of platelet/endothelial biomarkers even above the level expected in ACS. These findings may contribute to the unfavorable outcome associated with clinical depression in patients with ACS.

Altered expression and phosphorylation of myristoylated alanine-rich C kinase substrate (MARCKS) in postmortem brain of suicide victims with or without depression

Myristoylated alanine-rich C kinase substrate (MARCKS), an acidic, heat-stable protein, is involved in important physiological functions such as neurotransmitter release and re-uptake. It is also a substrate for phosphorylation by protein kinase C (PKC) and has been shown to play a role in the pathophysiology of mood disorders. In this study, protein and mRNA expression of MARCKS as well as phosphorylation of MARCKS were determined in the prefrontal cortex (PFC) and hippocampus of postmortem brain obtained from suicide victims, with or without depression, and normal control subjects. There were no significant differences in mRNA and protein levels of MARCKS between suicide subjects and controls. However, protein levels of MARCKS were significantly increased in the membrane but not in cytosol fraction of PFC and hippocampus obtained from depressed suicide subjects as compared to normal controls. When PKC-mediated MARCKS phosphorylation was determined, it was observed that MARCKS phosphorylation was significantly decreased in the membrane fraction of PFC and hippocampus obtained from total suicide subjects as well as depressed and non-depressed suicide subjects compared with control population. Although the mechanism of such alterations in MARCKS in depressed and non-depressed suicide subjects is not clear, results of the present study indicate that an increase in membrane MARCKS is associated with depressed suicide victims and a decrease in MARCKS phosphorylation may be a common feature of suicide victims independent of diagnosis.

The serotonin-2A receptor polymorphism and clinical symptoms in mood disorders, schizophrenia and alcohol dependence in Japan

In the past, there have been many epidemiological and genetic studies of mood disorders, schizophrenia, and alcohol dependence, and in this study, the human serotonin 2A receptor (5-HTR2A) polymorphism was examined in 80 patients with mood disorders, 50 patients with schizophrenia and 41 patients with alcohol dependence. 5-HTR is related to affectivity, regulation, and pharmacologic effects of antidepressant, anti-anxiety and antipsychotic medications. The polymorphism in 5-HTR2A (102T/C, -1438 A/G) was identified by the polymerase chain reaction (PCR), followed by restriction fragment length polymorphism (RFLP). The results suggest that 5-HTR2A (102T/C, -1438G/A) polymorphism might not be associated with susceptibility to schizophrenia or mood disorders, and it might not be a risk factor contributing to alcohol dependency. We found that the 102T/C polymorphism was in linkage disequilibrium with the -1438G/A polymorphism in psychosis (mood disorder, schizophrenia, and alcohol dependence) and in health controls. Further studies are needed to determine whether or not the novel serotonin receptor (5-HTR) polymorphism reflects the pathogenesis of schizophrenia, mood disorders, and alcohol dependence.

Altered 5-HT-induced calcium response in the presence of staurosporine in blood platelets from bipolar disorder patients

We have reported that the platelet intracellular calcium (Ca) mobilization after stimulation by serotonin (5-HT) is specifically enhanced in bipolar disorder among various psychiatric disorders, compared with that in normal control. To explore the mechanisms of enhanced Ca response to 5-HT in the platelets, we first examined the relation between the 5HT-elicited Ca mobilization and 5-HT(2A) receptor density using the platelets from 13 normal subjects. From this study, we found no significant correlation between two measures. Then, we investigated the effects of staurosporine, a protein kinase C (PKC) inhibitor, on Ca response to 5-HT in platelets from patients with major depressive disorder (unipolar), bipolar disorder, and normal controls. While 5-HT-induced Ca mobilization, in the presence of 100 nM staurosporine, was significantly attenuated in normal controls and patients with major depressive disorder, the inhibitory effect of staurosporine was not observed in bipolar disorder. These results suggest that the failure in inhibiting the platelet intracellular Ca response to 5-HT in bipolar disorder may be related to increased activity of PKC rather than increased 5-HT(2A) receptor number. Moreover, the trend of the Ca response towards staurosporine may become a specific biological marker for unipolar-bipolar dichotomy.

Prefrontal 5-HT2a receptor binding index, hopelessness and personality characteristics in attempted suicide

BACKGROUND

Depression, hopelessness, impaired problem solving capacities and deficient serotonergic functions have been identified as major causes of suicidal behaviour. In general, the relation between biological markers of attempted suicide and psychological functions has been investigated using indirect peripheral markers of, e.g. the serotonergic system. Recently, functional neuroimaging techniques with radioligands allow direct in vivo assessment of the neurobiological status of the central nervous system.

METHODS

We studied the binding index of serotonin-(2a) (5-HT(2a)) receptors in the frontal cortex of attempted suicide patients (n=9) and normal controls (n=13) using [123I]5-I-R91150, a highly selective 5-HT(2a) receptor ligand. Moreover, we measured personality characteristics (using Cloninger's Temperament and Character Inventory) and levels of hopelessness (using Beck's Hopelessness Scale), and studied the association between 5-HT(2a) receptor binding index, hopelessness and these personality dimensions.

RESULTS

When compared to normal controls, attempted suicide patients had a significantly lower binding potential of frontal 5-HT(2a) receptors, a higher level of hopelessness, a higher score on the temperament dimension harm avoidance and lower scores on the character dimensions self-directedness and cooperativeness. A significant correlation was found between harm avoidance, hopelessness and binding index in the population of patients that attempted suicide.

LIMITATIONS

The limited number of patients and potential ingestion of psychotropic drugs may influence the results of the study.

CONCLUSIONS

Lower central serotonergic function, hopelessness and harm avoidance are interrelated phenomena, which may increase the probability of the occurrence of attempted suicide.

Cytoskeleton of human mononuclear cells as a possible peripheral marker for phenylalanine neurotoxicity in PKU

In this work we tested human mononuclear cells as a peripheral marker to study neurotoxicity of phenylalanine (Phe). Slices of cerebral cortex of rats or human mononuclear cells were incubated with different concentrations of Phe and/or Ala in the presence of 32P-orthophosphate, the cytoskeletal fraction was extracted, and the radioactivity incorporated into intermediate filament proteins was measured. Our results show that 2 mM Phe as well as 1 mM Ala are effective in increasing the 32P in vitro incorporation into IFs in both tissues. When cerebral cortex slices or mononuclear cells were incubated with different concentrations of Phe and/or Ala, the effects on the 32P in vitro incorporation into IF proteins was compatible with an antagonistic mechanism of action of the two amino acids on the enzymes of the phosphorylating system. In addition, these blood cells may be a possible peripheral marker to study neurotoxicity of Phe in patients with PKU.

Platelet serotonin transporter in schizophrenic patients with and without neuroleptic treatment

Among various hypotheses put forth to account for the etiology of schizophrenia, the abnormal function of serotonergic system has recently gained marked interest. Our previous study showed that drug-free schizophrenic patients had a significant increase in maximum numbers (B(max)) of platelet 5-HT(2A) receptors that declined to normal level after treatment with different neuroleptic drugs. To elucidate the role of the serotonin system in schizophrenia, the serotonin transporters on human platelets were examined in this study. Platelet serotonin transporters obtained from normal control subjects and schizophrenic patients were identified by using [(3)H]imipramine as the radioligand and fluoxetine to define the non-specific binding. The data showed that the mean B(max) of serotonin transporter sites for schizophrenic patients without neuroleptic therapy was significantly higher than in normal controls. The B(max) values for schizophrenic patients on phenothiazine, butyrophenone, thioxanthene and serotonin-dopamine antagonist (SDA) therapies were significantly lower than the B(max) values obtained from schizophrenic patients without neuroleptic therapy, and were comparable to those found in normal control subjects. The dissociation equilibrium constant (K(d)) values in all subject groups remained unchanged. The effect of various medication periods on platelet serotonin transporters was also studied. We found that, B(max) values of 1-4 weeks, 1-4 months, 4-12 months and >1 year of neuroleptic therapies were significantly decreased when compared with the unmedicated group. Significant reduction of brief psychiatric rating scale (BPRS) occurred in all types of neuroleptics and every period of drug treatments compared with the unmedicated group. The present results indicate that alteration of platelet serotonin transporters is associated with schizophrenia. Treatment with various types of neuroleptics suppresses the hypersensitivity of platelet serotonin transporters. The mechanisms of how neuroleptics achieve their therapeutic effects, whether they act via or modulate serotonin system in certain brain area, still need to be further evaluated.

Is there circannual variation of human platelet 5-HT(2A) binding in depression?

BACKGROUND

Seasonal variations in onset of mood disorders and in serotonergic function are reported, but their relationship is unclear.

METHODS

Circannual variation in platelet 5-HT(2A) binding was measured in 68 healthy subjects and 121 patients with a major depressive episode. In 73 patients the current episode began during Spring or Fall.

RESULTS

Significant, but different, circannual variations were found in patients compared with controls. Controls had two peaks of B(max), one in Spring and another in Fall. Fall and Winter K(D) was 41% lower compared with Spring and Summer K(D). Patients had a peak of B(max) in early Spring and a lesser one in late Fall. B(max) during Spring and Fall was 12% higher compared with Winter and Summer. K(D) was higher during October through February compared with the rest of the year. B(max) in patients was higher compared with controls in March. The opposite difference was observed in September-December. These differences from controls were mostly due to patients with an onset of the current major depressive episode during Spring or Fall.

CONCLUSIONS

Patients with a major depressive episode differed from controls in circannual variation of platelet 5-HT(2A) binding. This may reflect a vulnerability to seasonal effects in patients with mood disorders.

Association of 5-HT(2A) receptor gene polymorphism with major affective disorders: the case of a subgroup of bipolar disorder with low suicide risk

BACKGROUND

The implication of serotonin in suicide and affective disease explains why the 5-HT(2A) receptor gene has been proposed as a candidate gene in these disorders, although with conflicting results.

METHODS

We analysed the distribution of the 5-HT(2A)-1438A/G genetic polymorphism in 192 patients with major affective disorder (127 bipolar disorders and 65 unipolar disorders) compared to 142 healthy control subjects.

RESULTS

We found a higher frequency of the A allele in affected patients than in control subjects (p =.034), this difference being particularly striking for the subgroup of patients with type I bipolar disorder (p =.015). Patients with no personal and/or familial history of suicide attempts mainly accounted for the excess of the A allele in affected patients.

CONCLUSIONS

The association detected in this study suggests that the 5-HT(2A) receptor gene may play a role in the genetic susceptibility to bipolar disorder, through a specific subgroup of bipolar type I patients with lower risk of suicidal behavior.

Effects of imipramine and lithium on wet-dog shakes mediated by the 5-HT2A receptor in ACTH-treated rats

We examined the influence of imipramine and lithium on wet-dog shakes induced by the (+/-)-DOI, 5-HT2A receptor agonist in adrenocorticotropic hormone (ACTH)-treated rats. The administration of imipramine for 14 days decreased the (+/-)-DOI-induced wet-dog shakes response; chronic administration of lithium for 14 days, however, had no effect. Chronic ACTH (100 microg/rat sc) treatment increased the wet-dog shake response induced by (+/-)-DOI. This effect of ACTH for 14 days, increasing the (+/-)-DOI-induced wet-dog shakes, was not inhibited by a 14-day administration of imipramine. Chronic coadministration of imipramine and lithium, lasting 14 days, decreased the wet-dog shakes response induced by (+/-)-DOI in rats treated with ACTH for 14 days. These findings indicate that lithium inhibits the hyperfunction of the 5-HT2A receptor in rats treated with ACTH when coadministered with imipramine.

Understanding the neurobiology of suicidal behavior

Our current knowledge about the neurobiology of suicide is still limited. Technical limitations and the complexity of the CNS are major obstacles. However, there is evidence for a hereditary disposition to suicide, which appears to be independent of diagnosis. Clinical, postmortem, genetic, and animal studies suggest that serotonin has a central role. The main regions of interest in the CNS have been the dorsal and median raphe nuclei in the midbrain that host the main serotonergic cell bodies and the prefrontal cortex, particularly the ventral PFC, innervated by the serotonergic system. In vivo and postmortem studies indicate serotonergic hypofunction in suicide and serious suicide attempts. This deficiency in turn can lead to a predisposition to impulsive and aggressive behavior, probably due to a breakdown in the inhibitory function of the ventral prefrontal cortex as a result of less serotonin input. In the context of this predisposition and the development of mental illness or other life stressors, the individual is at risk of acting on suicidal thoughts. Such deficient serotonin input into the PFC may arise as a result of genetic, parenting, head injury, and other effects. Identifying psychiatric, social, and environmental predictors of suicide are studied to improve prediction and prevention of suicide. A better understanding of the neurobiology of suicide can help detect at risk populations and help develop better treatment interventions.

Influence of ACTH on the effects of imipramine, desipramine and lithium on duration of immobility of rats in the forced swim test

We examined the effects of adrenocorticotropic hormone (ACTH) on the immobilization of rats in the forced swim test with the administration of imipramine, desipramine, or lithium. A single administration of either imipramine (10-30 mg/kg, i.p.) or desipramine (30 mg/kg, i.p.) significantly decreased the duration of immobility in normal rats in a dose-dependent manner. Lithium (10-100 mg/kg, p.o.), however, had no affect on the performance of rats in the forced swim test. ACTH (100 microg/day), administered subcutaneously to rats for 1, 3, 7, and 14 days, had no apparent effect on the duration of immobility in this test. The immobility-decreasing effect induced by a single administration of either imipramine (10-30 mg/kg, i.p.) or desipramine (30 mg/kg, i.p.) was blocked by chronic administration of ACTH for 3-14 days. The reduction of immobility, induced by chronic administration of imipramine (10 mg/kg, i.p.) for 15 days, was blocked by treatment with ACTH for 14 days. When lithium (100 mg/kg, p.o.) was administered for 15 days concurrently with imipramine (10 mg/kg, i.p.), we observed a significant decrease in immobility in rats treated with ACTH for 14 days. We suggest that chronic treatment of rats with ACTH may prove to be an effective model of tricyclic antidepressants-treatment-resistant depression.

5-HT2A receptor gene promoter polymorphism -1438A/G and bipolar disorder

Genetic factors, such as the genes involved in the serotonin pathway, probably play an important role in the pathogenesis of bipolar disorder, and serotonin type 2A (5-HT2A) receptor gene promoter polymorphism -1438A/G has been reported. This study investigated the association between -1438A/G polymorphism of 5-HT2A receptor gene promoter and bipolar disorder in a Korean population. Using the polymerase chain reaction, -1438A/G polymorphism typed in 142 patients with bipolar disorder and in 148 normal control subjects. Differences in genotype distributions and allele frequencies of -1438A/G between patients with bipolar disorder and normal control subjects were tested for significance using the chi-squared test. There were significant differences in genotype distributions [chi2 = 9.697, degrees of freedom (df) = 2, P = 0.008] and allele frequencies (chi2 = 7.284, df = 1, P = 0.007) of -1438A/G between patients with bipolar disorder and normal control subjects. Although further studies are necessary, these results in a Korean population suggest that -1438A/G polymorphism of 5-HT2A receptor gene promoter may be causally related to the development of bipolar disorder.

MRI correlates of suicide attempt history in unipolar depression

BACKGROUND

Suicide represents a major health problem in the United States, and prediction of suicide attempts is difficult. No structural neuroimaging studies have been done to specifically examine findings in patients who have attempted suicide. The objective of this study was to compare MRI findings in unipolar patients with and without a history of a suicide attempt.

METHODS

In this post hoc analysis, 20 unipolar subjects with a history of a suicide attempt were matched by age and gender to unipolar subjects without a history of an attempt. Subjects were also matched on parameters such as cardiovascular history, electroconvulsive treatment history, and history of psychosis. Subjects with a history of any neurologic condition were excluded. There were no significant differences in age of onset of depression, number of episodes of depression, and Hamilton Depression scores between the two groups. T2-weighted magnetic resonance imaging (MRI) scans were rated using the Coffey and Boyko rating scales.

RESULTS

Unipolar patients with a history of a suicide attempt demonstrated significantly more subcortical gray matter hyperintensities compared with patients without such a history.

CONCLUSIONS

Patients with abnormal MRI findings may be at higher risk for mood disorders and suicide attempts because of disruption of critical neuroanatomic pathways. Gray matter hyperintensities in the basal ganglia may be especially associated with risk for suicide attempts.

Platelet inhibition by sertraline and N-desmethylsertraline: a possible missing link between depression, coronary events, and mortality benefits of selective serotonin reuptake inhibitors

Recently, clinical depression has been identified as an independent risk factor for increased mortality in patients following acute coronary events. Although the underlying mechanisms of this link remain uncertain, increased platelet activity has been suggested but never proven as the mechanism responsible for this association. Sertraline hydrochloride is a selective serotonin reuptake inhibitor (SSRI), and is an effective antidepressant agent. Its major liver metabolite, N-desmethylsertraline (NDMS), is known to be neurologically inactive. We assessed the in vitro effects of escalating concentrations of sertraline and NDMS on human platelets by aggregometry in plasma and whole blood, by expression of major surface receptors with flow cytometry in washed cells and in the whole blood, and quantitatively by various platelet function analysers in healthy volunteers and patients with coronary artery disease. Pretreatment of blood samples with sertraline and NDMS resulted in a dose-dependent inhibition of platelet-rich plasma aggregation induced by 5 microM ADP (P =, 0.002), by 10 microM ADP (P = 0.0017), by collagen (P = 0.008), and by thrombin (P = 0.026). Whole blood platelet aggregability was also significantly reduced when induced by 20 microM ADP (P = 0.006), and by collagen (P = 0.01). Surface expression of CD9 (P = 0.004), GP Ib (P = 0.0001), GP IIb/IIIa (P = 0.007), VLA-2 (P = 0.01), P-selectin (P = 0.02), and PECAM-1 (P = 0.01), but not the vitronectin receptor, was also reduced in sertraline and NDMS pretreated washed platelets. Whole blood flow cytometry revealed significant inhibition of GP IIb/IIIa (P = 0.008), and P-selectin expression (P = 0.0001) in NDMS treated samples. Closure time was delayed for the collagen-ADP cartridge (P = 0.009), and for the collagen-epinephrin cartridge (P = 0.01), indicating platelet inhibition in whole blood under high shear conditions. Rapid platelet-function assay revealed a decreased (P = 0.002) ability of platelets to agglutinate fibrinogen-coated beads, suggesting GP IIb/IIIa inhibition. Both sertraline, and its neurologically inactive metabolite NDMS, exhibited significant dose-dependent inhibition of human platelets. The documented anti-platelet effects of sertraline and NDMS may be directly related to the mortality benefits of SSRIs after ischemic events including myocardial infarction and stroke.

Prospective study of depressive symptoms and risk of stroke among japanese

BACKGROUND AND PURPOSE

We sought to examine the relationship between depressive symptoms and the incidence of stroke among Japanese men and women.

METHODS

A 10.3-year prospective study on the relationship between depressive symptoms and the incidence of stroke was conducted with 901 men and women aged 40 to 78 years in a rural Japanese community. Depressive symptoms were measured at baseline with the use of the Zung Self-Rating Depression Scale (SDS). The incidence of stroke was ascertained under systematic surveillance.

RESULTS

During the 10-year follow-up, 69 strokes (39 ischemic strokes, 10 intracerebral hemorrhages, 10 subarachnoid hemorrhages, and 10 unclassified strokes) occurred. Age- and sex-adjusted prevalence of mild depression (SDS scores >/=40) at baseline was 25% among subjects with incident stroke and 12% among subjects without stroke (P<0.01). Persons with SDS scores in the high tertile had twice the age- and sex-adjusted relative risk of total stroke as those with scores in the low tertile. The excess risk was confined to ischemic stroke. After we adjusted for body mass index, systolic blood pressure level, serum total cholesterol level, cigarette smoking, current treatment with antihypertensive medication, and history of diabetes mellitus, these relative risks remained statistically significant for total stroke (1.9; 95% CI, 1.1 to 3.5) and ischemic stroke (2.7; 95% CI, 1.2 to 6.0).

CONCLUSIONS

Depressive symptoms predict the risk of stroke, specifically ischemic stroke among Japanese.

Effect of acute lipopolysaccharide administration on (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2 aminopropane-induced wet dog shake behavior in rats: comparison with body weight change and locomotor activity

1. Several reports have shown that serotonin (5-HT)2A receptor density and its function are altered after physiological or pharmacological stress. To examine whether an acute administration of lipopolysaccharide (LPS), a bacterial endotoxin, affected 5-HT2A receptor function, wet dog shakes of male Wistar rats were observed after a subcutaneous injection of DOI, a 5-HT2A receptor agonist following LPS treatment. Body weight change and locomotor activity were also observed. 2. DOI (1 mg/kg)-induced WDS significantly decreased after 400 or 1000 microg/kg LPS treatment compared with that of control rats 1 and 3 hr after injection, and WDS completely recovered 8 hr after LPS treatment. Treatment with 10 mg/kg indomethacin (IND) or 1 mg/kg naltrexone (NLTX) canceled the effect of 400 microg/kg LPS on DOI-induced WDS. 3. Body weight decrease was significantly greater in LPS-treated rats compared with control rats 3, 5 and 8 hr after treatment. Treatment with IND (10 mg/kg) significantly recovered the reduction in body weight induced by 400 microg/kg LPS. Treatment with NLTX (1 mg/kg) also prevented the LPS effect on body weight decrease. 4. Eight hr after treatment with LPS (400 microg/kg), the rats showed significant attenuation of locomotor activity. IND (10 mg/kg) treatment abolished the inhibitory effect of LPS on locomotor activity, and NLTX (1 mg/kg) also improved the decrease in locomotion 8 hr after LPS treatment. 5. Plasma tumor necrosis factor (TNF)-alpha concentration dramatically increased 1 hr after the injection of 400 microg/kg LPS, and returned almost to the basal level 3 hr later. Next, rats were injected with 50 microg/kg TNF-alpha intraperitoneally, and body weight change and DOI-induced WDS was determined 3 hr after TNF-alpha injection. Body weight loss was significantly greater in rats treated with TNF-alpha. On the other hand, DOI-induced WDS was not altered when rats were treated with TNF-alpha. 6. These results suggest that acute treatment with LPS inhibited 5-HT2A receptor-mediated behavior via cyclooxygenase and opioid receptor activation, but that the inhibition of the WDS by LPS appears to be independent of TNF-alpha production.

Serotonin 5-HT2A receptor binding in platelets from patients with Alzheimer's disease or vascular dementia

It is well known that abnormalities in the brain serotonin system exist in patients with dementia. The present study was performed in order to investigate whether a peripheral serotonin system marker, the platelet 5-HT2A receptor, is affected in dementia. Thirty-eight patients with Alzheimer's disease (AD), 13 patients with vascular dementia, and 40 healthy controls were included in the study. There were no significant differences in receptor density for 5-HT2A receptor binding between the groups. Affinity of the radioligand to the receptor was significantly lower in AD than in vascular dementia and in the controls (p = .006 and p = .003, respectively), whereas there was no significant difference between the vascular dementia group and the control group. In 12 patients, treatment with citalopram was started due to depression or agitation. This treatment significantly reduced the Behavioral Pathology in Alzheimer's Disease Rating Scale scores (p = .001), but did not affect the platelet 5-HT2A receptor status. There was no correlation between 5-HT2A receptor status before treatment and the therapeutic effect of citalopram. The study indicates that platelet 5-HT2A receptor status is of limited value as a peripheral marker in dementia.

Altered 5-HT(2A) binding sites and second messenger inositol trisphosphate (IP(3)) levels in hippocampus but not in frontal cortex from depressed suicide victims

The binding parameters of 5-HT(2A) and levels of its second messenger, 1,4,5-trisphosphate (IP(3)), were simultaneously studied in frontal cortex and hippocampus from the brains of 18 control subjects and 18 depressed suicide victims. All suicides met DSM-III-R criteria for depressive symptoms, suffered a violent death and had not taken any antidepressant drugs for at least 6 months prior to death. A significant decrease in the number of 5-HT(2A) binding sites (154+/-22 vs. 254+/-36 fmol/mg), together with a significantly lower apparent affinity constant (1.02+/- 0.08 vs. 1. 36+/-0.09 nM), was detected in hippocampus but not in frontal cortex from the depressed suicides compared to the control subjects. Furthermore, IP(3) concentrations were significantly increased in hippocampus (3.2+/-0.3 vs. 2.1+/-0.3 pmol/g) but not in frontal cortex (1.3+/-0.3 vs. 2.7+/-0.5 pmol/g) from the suicide victims. The reported results may indicate a significant hypersensitivity of the 5-HT(2A) postsynaptic receptor located in the hippocampus from depressed suicide victims, giving rise to an enhancement of its intracellular signaling system with higher IP(3) production.

Platelet 5-HT(2A) receptors in schizophrenic patients with and without neuroleptic treatment

It has been suggested that abnormal function of the serotonergic system may be implicated in the pathophysiology of schizophrenia. In order to examine the role of this system in schizophrenia, we have determined 5-HT(2A) receptors on human platelets of 20 control subjects and 37 schizophrenic patients by using [3H]spiperone and ketanserin. The data showed that the maximum number (B(max)) of 5-HT(2A) receptors for schizophrenic patients without neuroleptic therapy was significantly higher than that for control subjects. The B(max) values for [3H]spiperone binding to platelets of schizophrenic patients on butyrophenone, phenothiazine, benzisoxazole and thioxanthene therapies were significantly lower than those obtained from the drug-free group, but were comparable to control values. The effect of various medication periods on platelet 5-HT(2A) receptors was also examined. We found that after 2-4 weeks, 1-4 months, 4-12 months and more than 1 year of neuroleptic treatments, the B(max) values were significantly decreased when compared with values in the drug-free group. The present results indicate that treatment with various types of neuroleptics decreases the hypersensitivity of platelet 5-HT(2A) receptors. Significant clinical improvements occurred in all types of neuroleptic-treated groups and for all different treatment durations in this study. The precise mechanisms of how neuroleptics achieve their therapeutic effects still need to be further delineated.

A review of the role of serotonin receptors in psychiatric disorders

Serotonin (5-hydroxytryptamine, 5-HT) mediates a wide variety of physiological functions by activating multiple receptors, and abnormalities of these receptor systems has been implicated in many psychiatric disorders including anxiety, depression, psychosis, migraine, disorders of sexual functioning, sleep, cognition, and feeding. Many of the currently used treatments for these disorders act by affecting the serotonergic system. Observation of serotonin receptor alterations, before and following effective treatments, may yield important insights into the aetiology of these psychiatric disorders and may ultimately lead to more selective and effective therapies. Copyright 2000 John Wiley & Sons, Ltd.

Platelet Na+, K+-ATPase activity as a possible peripheral marker for the neurotoxic effects of phenylalanine in phenylketonuria

The in vitro effects of phenylalanine or alanine alone or combined on Na+, K+-ATPase activity in membranes from human platelets were investigated. The enzyme activity was assayed in membranes prepared from platelet-rich plasma of healthy donors. Phenylalanine or alanine were added to the assay to final concentrations of 0.3 to 1.2 mM, similar to those found in plasma of phenylketonuric patients. Phenylalanine inhibited Na+, K+-ATPase activity by 20-50% [F(4,25)=11.47 ; p<0.001]. Alanine had no effect on Na+, K+-ATPase activity but when combined with phenylalanine prevented the enzyme inhibition. These results, allied to others previously reported on brain Na+, K+-ATPase activity, may reflect a general inhibitory effect of phenylalanine on this important enzyme activity. Therefore, it is possible that measurement of Na+, K+-ATPase activity in platelets from PKU patients may be a useful peripheral marker for the neurotoxic effects of phenylalanine.

Depression in patients with cardiac disease: a practical review

Some degree of depression affects at least 30% of hospitalized patients with coronary artery disease (CAD), and is associated with increased risks of mortality and continuing depression over at least the first year following hospital discharge. Despite its consequences for prognosis and quality of life, depression is underrecognized and undertreated in cardiac patients. The diagnosis of depression is complicated in patients with medical illness. Their symptoms can reflect physical as well as psychological complaints. Many CAD patients resist the idea of additional medications, and drug interactions can be problematic for those willing to accept antidepressant treatment. Finally, depression tends to recur. Its successful treatment requires a long-term commitment from both physician and patient. This article examines the special challenges involved in diagnosing depression in patients with CAD, outlines available psychotherapeutic and pharmacological treatments, and considers the issues involved in deciding which patients to treat, with what approach, and for how long.

Methodological considerations for the human platelet 5-HT2A receptor binding kinetic assay

Analysis of an extensive database of human platelet 5-HT2A receptor binding assays has been conducted in order to identify factors that may affect the assay results. Despite anecdotal reports that storage of frozen platelet pellets may affect 5-HT2A binding affinity and capacity, no quantitative study has been reported in the literature. Analysis of binding data for 373 frozen samples with a storage time up to three years is presented in this paper. It is shown that prolonged storage significantly decreases binding. The loss of binding capacity begins in the first six month of storage. Bmax declines by half after 17 month. The impact of storage time on the binding affinity is much smaller. There is only about 20% increase in the value of affinity K(D) during the half-life of Bmax. Differences in sample storage time may partly explain discrepancies in results between different research groups. Nonspecific binding due to binding to filter material diminishes accuracy and reliability of the binding assays as a result of a decrease in the ratio of specific to nonspecific ratio. A data analysis based on our suggested mathematical model shows that this effect depends on tissue concentration in test tube and becomes pronounced when the concentration is below 0.1 mg protein/ml (at 0.2 nM of ligand). Above 0.1 mg protein/ml, percentage of specific to total binding exceeds 65%, which is an acceptable level for the ratio. The majority of the binding studies reported in the literature employed a tissue concentration more than 0.5 mg/ml, well above the minimal limit sufficient for a reliable assay. However, development of microassays to conserve precious tissue must take the limit into consideration.

Effect of lithium carbonate on the enhancement of serotonin 2A receptor elicited by dexamethasone

The purpose of this study was to investigate whether chronic dexamethasone (Dex) administration induces serotonin (5-HT) 2A receptor supersensitivity and if chronic lithium carbonate (Li) administration contributes to the normalization of 5-HT2A receptor supersensitivity induced by Dex in rat brain. We investigated the effects of a 14-day administration of Dex and/or Li on changes in body weight (BW), on plasma corticosterone levels, on plasma lithium levels, on 5-HT2A receptor binding sites, and on (+/-)-1-(2, 5-dimethoxy-4-iodophenyl)-2 aminopropane (DOI)-induced wet dog shake (WDS), which is mediated by 5-HT2A receptor in rats. Dex significantly reduced the BW of rats. Li did not have any effect on BW gain and did not prevent the BW loss induced by Dex. The plasma corticosterone levels of rats treated with Dex were too low to be detected. Li did not have any effect on corticosterone levels and did not prevent the decrease in the corticosterone levels induced by Dex. Six hours after the last treatment, the plasma lithium levels of rats treated with Li were significantly higher than those of rats treated with Dex/Li. Chronic Dex administration resulted in a significant increase in the density (B(max)) of the 5-HT2A receptor without a significant change in the affinity (K(d)). The increase in the B(max) induced by Dex was not prevented by chronic combined treatment with Dex and Li. Chronic Dex administration potentiated the WDS, and this increase was prevented by chronic combined treatment with Dex and Li. Chronic Li administration did not have any effect on WDS. These results indicate that chronic Li administration may improve the supersensitivity of the 5-HT2A receptor elicited by chronic Dex administration without decreasing the density of the 5-HT2A receptor, and the effect of Li was also independent of hypothalamo-pituitary-adrenal axis function.

The current status of the platelet 5-HT(2A) receptor in depression

The author reviews the current status of the platelet serotonin (5-HT)(2A) receptor in depression. Considered are studies of receptor binding, and 5-HT-induced platelet activation and aggregation. 5-HT(2A) receptor density tends to increase in depression, although this more clearly relates to suicidality than depression per se. Indeed, data are consistent with the hypothesis that increased density of platelet 5-HT(2A) receptors may be a marker for increased risk of suicide. 5-HT-induced calcium mobilization is enhanced in unipolar depression; however, unlike in bipolar depression, baseline calcium levels are not. Despite inconsistencies, 5-HT-induced aggregation appears inhibited in depression. This may manifest as a relative inhibition, i.e. no change in aggregation response despite a higher density of 5-HT(2A) receptors. The inhibited aggregation response is state dependent, and acute phase proteins or components of the stress response may be factors. It is unclear if differences between depressed and normal subjects in disposition of 5-HT(2A) receptors are generally indicative of traits or states. Nonetheless, there is little evidence that the degree of departure from normal density or activity of platelet of 5-HT(2A) receptors reflects severity of depression.