Marked reduction in the number of platelet-tritiated imipramine binding sites in geriatric 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.

Are the changes in the peripheral brain-derived neurotrophic factor levels due to platelet activation?

Brain-derived neurotrophic factor (BDNF) plays an important role in central nervous system development, neurogenesis and neuronal plasticity. BDNF is also expressed in several non-neuronal tissues, and it could play an important role in other processes, such as cancer, angiogenesis, etc. Platelets are the major source of peripheral BDNF. However, platelets also contain high amounts of serotonin; they express specific surface receptors during activation, and a multitude of pro-inflammatory and immunomodulatory bioactive compounds are secreted from the granules. Until recently, there was insufficient knowledge regarding the relationship between BDNF and platelets. Recent studies showed that BDNF is present in two distinct pools in platelets, in α-granules and in the cytoplasm, and only the BDNF in the granules is secreted following stimulation, representing 30% of the total BDNF in platelets. BDNF has an important role in the pathophysiology of depression. Low levels of serum BDNF have been described in patients with major depressive disorder, and BDNF levels increased with chronic antidepressant treatment. Interestingly, there is an association between depression and platelet function. This review analyzed studies that evaluated the relationship between BDNF and platelet activation and the effect of treatments on both parameters. Only a few studies consider this possible confounding factor, and it could be very important in diseases such as depression, which show changes in both parameters.

Platelet aggregation and mental stress induced myocardial ischemia: Results from the Responses of Myocardial Ischemia to Escitalopram Treatment (REMIT) study

BACKGROUND

Mental stress-induced myocardial ischemia (MSIMI) is common in patients with ischemic heart disease (IHD) and associated with a poorer cardiovascular prognosis. Platelet hyperactivity is an important factor in acute coronary syndrome. This study examined associations between MSIMI and resting and mental stress-induced platelet activity.

METHODS

Eligible patients with clinically stable IHD underwent a battery of 3 mental stress tests during the recruitment phase of REMIT study. MSIMI was assessed by echocardiography and electrocardiography. Ex vivo platelet aggregation in response to ADP, epinephrine, collagen, serotonin, and combinations of serotonin plus ADP, epinephrine, and collagen were evaluated as was platelet serotonin transporter expression.

RESULTS

Of the 270 participants who completed mental stress testing, and had both resting and post-stress platelet aggregation evaluation , 43.33% (n=117) met criteria for MSIMI and 18.15% (n=49) had normal left ventricular response to stress (NLVR). The MSIMI group, relative to the NLVR groups, demonstrated heightened mental stress-induced aggregation responses, as measured by area under the curve, to collagen 10μM (6.95[5.54] vs. -14.23[8.75].; P=0.045), epinephrine 10μM (12.84[4.84] vs. -6.40[7.61].; P=0.037) and to serotonin 10 μM plus ADP 1 μM (6.64[5.29] vs. -27.34[8.34]; P<.001). The resting platelet aggregation and serotonin transporter expression, however, were not different between the two groups.

CONCLUSIONS

These findings suggest that the dynamic change of platelet aggregation caused by mental stress may underlie MSIMI. While the importance of these findings requires additional investigation, they raise concern given the recognized relationship between mental stress-induced platelet hyperactivity and cardiovascular events in patients with IHD.

Hyperreactive platelet phenotypes: relationship to altered serotonin transporter number, transport kinetics and intrinsic response to adrenergic co-stimulation

The mechanism underlying a hyperreactive platelet phenotype remains unknown. Since serotonin has been shown to influence platelet biology and atherothrombosis, we sought to investigate the association of platelet serotonin transporter number, binding affinity, and uptake kinetics with platelet aggregation. A total of 542 healthy volunteers had light transmittance platelet aggregometry measured in response to varying concentrations of epinephrine, serotonin, epinephrine plus serotonin, ADP and collagen. Transporter-dependent serotonin uptake rate was determined (Vmax), as were serotonin transporter number (Bmax) and binding affinity (Kd) using 3H paroxetine binding in a homologous displacement assay, nonlinear regression and validated algorithms for kinetic modelling. Stimulation with submaximal (2μM) epinephrine concentration elicited a distinct, bimodal pattern of platelet aggregation in this population. In contrast, subjects exhibited minimal aggregation in response to serotonin alone. Co-stimulation with submaximal epinephrine and serotonin induced platelet aggregation to a level beyond that observed with either agonist alone and maintained a bimodal response distribution. Subjects with heightened (>60%) platelet aggregation to both epinephrine alone and epinephrine plus serotonin exhibited increased platelet serotonin uptake, and transporter number and affinity. In a population of healthy subjects, co-stimulation with submaximal concentrations of epinephrine and serotonin identifies a subset of individuals with a hyperreactive platelet aggregation profile that is associated with changes in platelet serotonin function.

Association of mean platelet volume with DSM-IV major depression in a large community-based population: the MELEN study

The relationship between major depression and increased platelet activity has been previously stated by several studies. This study sought to test the relationship between mean platelet volume (MPV)--an indicator of platelet activity--and major depression, in an adult Turkish population sample. Respondents were 2286 participants interviewed in a regional survey. The diagnosis of current (one month) major depression was made according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. MPV was measured along with total cholesterol, triglycerides, HDL-cholesterol, LDL-cholesterol, BMI, and waist circumference. Two hundred eighty-nine participants (12.5%) were diagnosed as having major depression. Patients with major depression were found to have increased MPV levels in comparison with participants without depression (p = 0.001). After excluding the subjects with risk factors capable of influencing platelet activity, MPV was still found to be elevated in patients with major depression compared with non-depressed individuals (p < 0.01). Linear regression analysis revealed a significant independent association of major depression with MPV levels (r = 0.123; p = 0.001). According to the findings of this study, increased MPV (or platelet activation) is associated with current (one month) diagnosis of major depression. Future research should investigate the effect of depression treatment on MPV.

Mean platelet volume in patients with major depression: effect of escitalopram treatment

BACKGROUND

The relationship between major depression and increased platelet activity has been previously indicated by several studies. The aims of this study were to examine mean platelet volume (MPV), which is an indicator of platelet activity, in patients with depression and investigate whether escitalopram treatment would affect MPV.

METHODS

Fifteen patients (11 women and 4 men) meeting the criteria for a current episode of major depressive disorder were recruited to the study and 17 physically and mentally healthy comparison subjects (11 women and 6 men). Mean platelet volume and platelet count of the controls and patients were measured upon entry to the study. After 8 weeks of open-label treatment with the selective serotonin reuptake inhibitor escitalopram (10-20 mg/d), the patients with depression were readmitted and the measurements were repeated.

RESULTS

At baseline, in comparison with the control group, the group with depression exhibited greater platelet activity as detected by increased MPV. After escitalopram treatment, the patients with depression exhibited significant reduction in MPV. There was also a significant decline in platelet count.

CONCLUSIONS

In this study, normalization of platelet activation is associated with escitalopram treatment for patients with depression. This finding may provide evidence for the use of escitalopram in patients with major depression and comorbid ischemic heart disease.

Mood disorder and epilepsy: a neurobiologic perspective of their relationship

Mood disorders are the most frequent psychiatric comorbidity in epilepsy, and in particular in temporal lobe epilepsy. For a long time, depressive disorders were considered to be the expression of a reactive process to the obstacles of a life with epilepsy Data obtained in the last two decades, however, have demonstrated biochemical, neuropathoiogical, and neurophysioiogic changes mediating the development of mood disorders, which in fact can be tested in animal models. Furthermore, there is also evidence that mood disorders and epilepsy have a complex relationship which is bidirectional; that is, not only are patients with epilepsy at greater risk of developing depression, but patients with depression have a higher risk of developing epilepsy. Such a relationship can only be explained by the existence of common pathogenic mechanisms that are operant in both conditions. These include changes in neurotransmitters, such as serotonin, norepinephrine, glutamate, and γ-aminobutyric acid. Such a bidirectional relationship also appears to have important clinical consequences. Indeed, patients with a history of mood disorders are twice as likely to develop pharmacoresistant epilepsy as those without such a history. These data are reviewed in this article.

Platelet and endothelial activity in comorbid major depression and coronary artery disease patients treated with citalopram: the Canadian Cardiac Randomized Evaluation of Antidepressant and Psychotherapy Efficacy Trial (CREATE) biomarker sub-study

BACKGROUND AND PURPOSE

Major depression is an independent risk factor for increased morbidity and mortality in patients with coronary artery disease (CAD). Increased platelet activity and vascular endothelial dysfunction are possible pathways through which depression may increase cardiovascular risk. Citalopram exhibits strong selective inhibition of human platelet activation, but little is known about its effects on vascular endothelium. We assessed whether treatment of depressed CAD patients with citalopram alters platelet/endothelial biomarkers. The study was performed within the framework of the CREATE trial.

METHODS

We assessed the effect of citalopram on P-selectin, beta-thromboglobulin (betaTG), soluble intercellular cell adhesion molecule-1 (sICAM-1), and total nitric oxide (tNO). Plasma samples were obtained at baseline and week 12 from subjects randomized to citalopram 20-40 mg daily (n = 36), or placebo (n = 21). Anticoagulants, aspirin, and clopidogrel were permitted.

RESULTS

Treatment with citalopram was associated with greater increase in tNO over 12 weeks compared to placebo (P = 0.005). There were no differences for the other biomarkers such as P-selectin (P = 0.70), betaTG (P = 0.46) and ICAM (P = 0.59).

CONCLUSION

Treatment with citalopram for 12 weeks in depressed CAD patients is associated with enhanced production of nitric oxide despite the co-administration of commonly prescribed anti-platelet regimens including aspirin and clopidogrel. Clinical implications of these findings are unclear, but improved endothelial function is implied by the increased NO production, suggesting that citalopram may be of particular benefit for patients with comorbid depression and vascular disease including CAD, stroke, peripheral artery disease, and diabetes.

The interaction of serotonin transporter gene polymorphisms and early adverse life events on vulnerability for major depression

Considerable literature supports the hypothesis of dysfunction in central nervous system serotonergic circuits in the pathophysiology of mood disorders, specifically major depression. Since the development of the selective serotonin (5-HT) reuptake inhibitors, a putative role for the 5-HT transporter (SERT) in the etiology of depression has been explored. The discovery of a functional SERT polymorphism has provided a novel tool to further scrutinize the role of serotonergic neurons in depression. This article reviews the burgeoning evidence of an interaction between early life stress and an SERT polymorphism on vulnerability to depression.

Association of corticotropin-releasing hormone receptor1 gene SNP and haplotype with major depression

The dysregulation of the activity of the hypothalamic-pituitary-adrenocortical (HPA) axis system is one of the major neuroendocrine abnormalities in major depression (MD). Many pieces of evidence supported that corticotropin-releasing hormone (CRH) play a role in the pathophysiology of major depression. In this article, whether genetic variations in the corticotropin-releasing hormone receptor1 (CRHR1) gene might be associated with increased susceptibility to major depression was studied by using a gene-based association analysis of single-nucleotide polymorphisms (SNPs). Three SNPs were identified in CRHR1 gene and genotyped in the samples of patients diagnosed with major depression and matched controls. We observed significant allele (P=0.0008) and genotype (P=0.0002) association with rs242939, and the haplotype defined by alleles G-G-T for the represent rs1876828, rs242939 and rs242941 was significantly over-represented in major depression patients compared to controls. These results support the idea that the CRHR1 gene is likely to be involved in the genetic vulnerability for major depression.

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.

Depression in epilepsy: a neurobiologic perspective

Depression is the most frequent psychiatric comorbidity in patients with epilepsy. By the same token, patients with depression are at higher risk of developing epilepsy than are controls. Such bidirectional relations raise the question of whether both disorders share common pathogenic mechanisms, presenting with common neurotransmitter abnormalities and involvement of the same neuroanatomic structures. In this article, some of the available data in support of this hypothesis are reviewed.

Alterations in platelet serotonin transporter binding in women with postpartum onset major depression

There is considerable debate as to whether postpartum depression (PPD) is biologically distinct from other depressive syndromes. Although abnormalities in serotonergic neural systems have repeatedly been reported in depression, few such studies have been conducted in PPD. In the present study, platelet serotonin transporter (SERT) binding was assessed using [(3)H]paroxetine in 14 depressed pregnant women, 31 normal healthy pregnant women, 39 depressed postpartum women, and 27 normal healthy postpartum women; all of the subjects were drug-free. Significant differences were detected among the 4 groups with respect to the dissociation constant (Kd) of platelet binding sites for [(3)H]paroxetine with the highest Kd values among those with PPD. The density (Bmax) of platelet binding sites for [(3)H]paroxetine did not differ between the study groups. These data suggest that PPD may be associated with unique alterations in serotonergic function that are specific to the puerperium.

Unipolar late-onset depression: A comprehensive review

Background

The older population increases all over the world and so also does the number of older psychiatric patients, which manifest certain specific and unique characteristics. The aim of this article is to provide a comprehensive review of the international literature on unipolar depression with onset at old age.

Methods

The authors reviewed several pages and books relevent to the subject but did not search the entire literature because of it's overwhelming size. They chose to review those considered most significant.

Results

The prevalence of major depression is estimated to be 2% in the general population over 65 years of age. The clinical picture of geriatric depression differs in many aspects from depression in younger patients. It is not yet clear whether it also varies across cultures and different socio-economic backgrounds. Biological data suggest that it is associated with an increased severity of subcortical vascular disease and greater impairment of cognitive performance. Many authors consider the existence of a somatic disorder to be related to the presence of depression in late life, even constituting a negative prognostic factor for the outcome of depression. Most studies support the opinion that geriatric depression carries a poorer prognosis than depression in younger patients. The therapeutic intervention includes pharmacotherapy, mainly with antidepressants, which is of established value and psychotherapy which is not equally validated.

Conclusion

A significant number of questions regarding the assessment and treatment of geriatric depression remain unanswered, empirical data are limited, and further research is necessary.

Common pathogenic mechanisms between depression and epilepsy: an experimental perspective

Affective disorders and the epilepsies appear to share partially similar pathogenic mechanisms. Predisposition to both disorders is determined genetically and experientially. A component of the shared predisposition appears to arise from noradrenergic and serotonergic deficits. Shared GABAergic deficits coupled with CRHergic and glutamatergic excesses may trigger and maintain seizures as well as dysfunctional affective episodes, albeit via dissimilar neuronal interplay.

Platelet/endothelial biomarkers in depressed patients treated with the selective serotonin reuptake inhibitor sertraline after acute coronary events: the Sertraline AntiDepressant Heart Attack Randomized Trial (SADHART) Platelet Substudy

BACKGROUND

Depression after acute coronary syndromes (ACSs) has been identified as an independent risk factor for subsequent cardiac death. Enhanced platelet activation has been hypothesized to represent 1 of the mechanisms underlying this association. Selective serotonin reuptake inhibitors (SSRIs) are known to inhibit platelet activity. Whether treatment of depressed post-ACS patients with SSRIs alters platelet function was not known. Accordingly, we serially assessed the release of established platelet/endothelial biomarkers in patients treated with sertraline vs placebo in the Sertraline AntiDepressant Heart Attack Randomized Trial (SADHART).

METHODS AND RESULTS

Plasma samples (baseline, week 6, and week 16) were collected from patients randomized to sertraline (n=28) or placebo (n=36). Anticoagulants, aspirin, and ADP-receptor inhibitors were permitted in this study. Platelet factor 4, beta-thromboglobulin (betaTG), platelet/endothelial cell adhesion molecule-1, P-selectin, thromboxane B2, 6-ketoprostaglandin F1a, vascular cell adhesion molecule-1, and E-selectin were measured by ELISA. Treatment with sertraline was associated with substantially less release of platelet/endothelial biomarkers than was treatment with placebo. These differences attained statistical significance for betaTG (P=0.03) at weeks 6 and 16 and for P-selectin (P=0.04) at week 16. Repeated-measures ANOVA revealed a significant advantage for sertraline vs placebo for diminishing E-selectin and betaTG concentrations across the entire treatment period.

CONCLUSIONS

Treatment with sertraline in depressed post-ACS patients is associated with reductions in platelet/endothelial activation despite coadministration of widespread antiplatelet regimens including aspirin and clopidogrel. The antiplatelet and endothelium-protective properties of SSRIs might represent an attractive additional advantage in patients with depression and comorbid coronary artery and/or cerebrovascular disease.

Depression in late life: review and commentary

Depression is perhaps the most frequent cause of emotional suffering in later life and significantly decreases quality of life in older adults. In recent years, the literature on late-life depression has exploded. Many gaps in our understanding of the outcome of late-life depression have been filled. Intriguing findings have emerged regarding the etiology of late-onset depression. The number of studies documenting the evidence base for therapy has increased dramatically. Here, I first address case definition, and then I review the current community- and clinic-based epidemiological studies. Next I address the outcome of late-life depression, including morbidity and mortality studies. Then I present the extant evidence regarding the etiology of depression in late life from a biopsychosocial perspective. Finally, I present evidence for the current therapies prescribed for depressed elders, ranging from medications to group therapy.

Human genetic variation and mental disorders

Despite extensive research, our knowledge of structural or functional pathology of severe mental disorders such as schizophrenia and major affective disorders is limited. The only etiological factor with reasonably firm foundation is inheritance, as evidenced by family, twin and adoption studies, however, the molecular basis of this heritability is not established yet. In the absence of clear knowledge about the biological substrate for these psychiatric disorders all the genes expressed in the human brain are potential candidate genes. Association studies analyze genetic variants (polymorphisms) in genes with presumed functional significance in the pathophysiology of the disease (candidate genes). These genetic studies compare the frequency of the hypothetical risk variant in people affected by the disease and in healthy control representatives of the same population. Also, simplex families with an affected child (trios) or with discordant affected offspring (quadruplets), can be used in the association studies. This strategy constitutes a tool to identify the small and moderate effects of genes in these complex phenotypes. Likewise, these kinds of studies could be useful to explain the effect of genes in some specific traits and symptoms present in functional psychoses. Some of our own results on serotoninergic system genes and major depression are included in this chapter as an example of case-control association developed studies in mental disorders.

Affective disorders in advanced cancer

Depression is a common complication of advanced cancer. Methods of accurate assessment and recognition are available. Risk factors for the development of depression have been identified. Pharmacologic and nonpharmacologic treatments for depression are often effective even in patients with advanced cancer.

Role of serotonergic and noradrenergic systems in the pathophysiology of depression and anxiety disorders

There is abundant evidence for abnormalities of the norepinephrine (NE) and serotonin (5HT) neurotransmitter systems in depression and anxiety disorders. The majority of evidence supports underactivation of serotonergic function and complex dysregulation of noradrenergic function, most consistent with overactivation of this system. Treatment for these disorders requires perturbation of these systems. Reproducible increases in serotonergic function and decreases in noradrenergic function accompany treatment with antidepressants, and these alterations may be necessary for antidepressant efficacy. Dysregulation of these systems clearly mediates many symptoms of depression and anxiety. The underlying causes of these disorders, however, are less likely to be found within the NE and 5HT systems, per se. Rather their dysfunction is likely due to their role in modulating, and being modulated by, other neurobiologic systems that together mediate the symptoms of affective illness. Clarification of noradrenergic and serotonergic modulation of various brain regions may yield a greater understanding of specific symptomatology, as well as the underlying circuitry involved in euthymic and abnormal mood and anxiety states. Disrupted cortical regulation may mediate impaired concentration and memory, together with uncontrollable worry. Hypothalamic abnormalities likely contribute to altered appetite, libido, and autonomic symptoms. Thalamic and brainstem dysregulation contributes to altered sleep and arousal states. Finally, abnormal modulation of cortical-hippocampal-amygdala pathways may contribute to chronically hypersensitive stress and fear responses, possibly mediating features of anxiety, anhedonia, aggression, and affective dyscontrol. The continued appreciation of the neural circuitry mediating affective states and their modulation by neurotransmitter systems should further the understanding of the pathophysiology of affective and anxiety disorders.

The platelet as a peripheral marker in psychiatric illness

The identification of peripheral markers of psychiatric illness is important if an improvement in the diagnosis and treatment of various diseases with overlapping symptomatology is desired. There are many disorders that not only have overlapping symptomatology, but also have similar biological disturbances. The functional capability of the neurons involved in the disease processes may be at the crux of the underlying pathology. The platelet intracellular calcium response to neurotransmitter stimulation has previously been used as a peripheral marker of psychiatric illness. This review discusses evidence in support of the extended use of the platelet as a peripheral marker. The use of the platelet intracellular calcium response to neurotransmitter stimulation as a state or trait marker in major depression, the specificity and selectivity of this response, and the possible use of the platelet as a peripheral marker in psychotic disorders such as schizophrenia, mania and psychotic depression are shown. Finally, a proposed mechanism for the association between certain psychiatric disorders and cardiovascular disease is discussed. Copyright 2001 John Wiley & Sons, Ltd.

The state of the serotonin transporter protein in the platelets of patients with somatoform [correction of somatiform] disorders

The role of the serotonin transporter protein (STP) in the development of somatoform [corrected] disorders was addressed in a correlational study of the levels of immunoreactive STP (IR-STP) using site-specific antibodies against the least conserved (among a group of other cotransporters) epitope at the C-terminal of STP and the level of anxiety symptoms in patients with somatoform [corrected] disorders. A total of 22 patients were studied, with DSM-IV diagnoses of somatoform [corrected] disorders, along with 32 mentally healthy subjects of comparable age and sex. Immunoblotting of IR-STP from patients from healthy donors produced a diffuse band between 68 and 105 kDal and a clear narrow band at 43 kDal. The 43-kDal IR-STP protein was almost completely absent from most patients, as compared with the levels of this protein in healthy donors. This result suggests an abnormality of STP processing or, perhaps, alternative splicing of the gene encoding STP in patients with somatoform [corrected] disorders, and this appears to reflect the dysfunction in serotoninergic transmission in the CNS in these patients.

Phosphorylation and sequestration of serotonin transporters differentially modulated by psychostimulants

Many psychotropic drugs interfere with the reuptake of dopamine, norepinephrine, and serotonin. Transport capacity is regulated by kinase-linked pathways, particularly those involving protein kinase C (PKC), resulting in transporter phosphorylation and sequestration. Phosphorylation and sequestration of the serotonin transporter (SERT) were substantially impacted by ligand occupancy. Ligands that can permeate the transporter, such as serotonin or the amphetamines, prevented PKC-dependent SERT phosphorylation. Nontransported SERT antagonists such as cocaine and antidepressants were permissive for SERT phosphorylation but blocked serotonin effects. PKC-dependent SERT sequestration was also blocked by serotonin. These findings reveal activity-dependent modulation of neurotransmitter reuptake and identify previously unknown consequences of amphetamine, cocaine, and antidepressant action.

Psychopharmacology of depression in the next millennium

Over the last half of the 20th century, there have been a series of psychopharmacologic strategies for treatment of depression. As we approach the next century, new therapies in varying stages of American release are being developed. This review will focus on information available for the following proposed antidepressants: 1) reboxetine, a norepinephrine selective reuptake inhibitor; 2) milnacipran, a combined serotonin/norepinephrine reuptake inhibitor; 3) a new enantiomer of fluoxetine, a selective serotonin reuptake inhibitor; 4) duloxetine, another combined serotonin/norepinephrine reuptake inhibitor; 5) sunepitron, a combined 5-HT1A agonist and a2 antagonist; and 6) MK-869, a substance P inhibitor. Finally, other possible developing directions will be reviewed, including corticotropin-releasing factor.

Reduced brain serotonin transporter availability in major depression as measured by [123I]-2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane and single photon emission computed tomography

BACKGROUND

Prior research has suggested reductions in the density of serotonin transporter (SERT) binding sites in blood platelets and post-mortem brain tissue of depressed patients. We sought to determine whether patients with unipolar major depression have diminished SERT availability as assessed by both brainstem [123I] beta-CIT SPECT and platelet [3H]paroxetine binding.

METHODS

Drug-free depressed and healthy subjects were injected with 211 +/- 22 MBq [123I] beta-CIT and imaged 24 +/- 2 h later under equilibrium conditions. A ratio of specific to nonspecific brain uptake (V3" = (brainstem-occipital)/occipital), a measure proportional to the binding potential (Bmax/Kd), was used for all comparisons.

RESULTS

Results showed a statistically significant reduction in brainstem V3" values in depressed as compared to healthy subjects (3.1 +/- .9 vs. 3.8 +/- .8, p = .02). Platelet [3H]paroxetine binding was not altered (Bmax = 2389 +/- 484 vs. 2415 +/- 538 fmol/mg protein, p = .91) and was not significantly correlated with brainstem [123I] beta-CIT binding (r = -0.14, p = .48).

CONCLUSIONS

These data are the first to suggest reductions in the density of brain SERT binding sites in living depressed patients. These findings provide further support for a preeminent role for alterations in serotonergic neurons in the pathophysiology of depression.

Sex steroid control of mood, mental state and memory

1. Sex steroid hormones exert profound effects on mood and mental state. Thus, in women, oestrogen is thought to protect against depression and delay the onset of schizophrenia and Alzheimer's disease. 2. Our studies in the female rat show that oestradiol, in its positive feedback mode for gonadotrophin release, increases the expression of genes for the 5-hydroxytryptamine 5-HT2A receptor and the serotonin transporter (SERT) in the dorsal raphe nucleus and the density of 5-HT2A receptor and SERT sites in regions of the forebrain that, in the human, are concerned with cognition, mental state, emotion and memory. 3. In the male rat, castration decreases while oestrogen and testosterone, but not 5 alpha-dihydrotestosterone (5 alpha-DHT), increase the density of 5-HT2A receptors in forebrain. The fact that 5 alpha-DHT has no effect suggests that the action of testosterone depends on its conversion to oestradiol by aromatase. 4. In intact rats, the density of 5-HT2A receptors in cerebral cortex is significantly higher in pro-oestrous female than in male and dioestrous female rats, showing that the spontaneous, preovulatory surge of oestradiol that reaches a peak at 12.00 h of pro-oestrus also increases the density of 5-HT2A receptors in cortex. 5. Oestrogen and testosterone (by way of its conversion to oestrogen) also stimulate the expression of the arginine vasopressin gene in the bed nucleus of the stria terminalis of the rodent, a mechanism that plays a key role in olfactory memory. 6. These actions of sex steroid hormones are discussed in the context of genomic versus non-genomic mechanisms, the recent discovery that there are two oestradiol receptors with different distributions in brain, the significance of our findings for our understanding of the control of mood, mental state and memory and the mechanism by which oestrogen stimulation of the 5-HT2A receptor could delay the onset of Alzheimer's disease.

Platelet serotonin transporter in depressed children and adolescents: 3H-paroxetine platelet binding before and after sertraline

OBJECTIVE

To evaluate serotonin transporter protein (5HTPR) binding in platelets from children and adolescents with major depression (MDD) compared to normal controls using the selective ligand 3H-paroxetine.

METHOD

Children and adolescents with MDD (n = 24) defined by DSM-III-R criteria and normal controls (n = 22) were compared by platelet 5HTPR kinetic analysis with the hypothesis that 5HTPR is reduced in MDD. A subset of MDD subjects (n = 18) continued to participate in a fixed-dose, open-label sertraline trial for 6 weeks followed by drug-free washout and repeated 5HTPR analysis.

RESULTS

Sex, prepubertal status, and age had no effect on 5HTPR. Medication-free MDD subjects differed from controls in reduced binding capacity (Bmax) (p < .001). Sertraline therapy decreased binding affinity from baseline non-selectively (p < .05), and Bmax elevation from baseline was associated with nonresponse and suicide attempt history.

CONCLUSION

Earlier literature in this population is replicated with regard to reduced platelet 5HTPR Bmax in MDD. Findings support a continuum of 5HTPR involvement in MDD across the developmental spectrum.

Serotonin transporter expression in rat brain regions and blood platelets: aging and glucocorticoid effects

Hyperactivity of the hypothalamus-pituitary-adrenal axis is more common in elderly depression than in younger cohorts and glucocorticoids are known to influence serotonergic systems. The current study explores the interaction of glucocorticoids with aging on serotonin transporter expression and function. Continuous infusions of dexamethasone (26 days) reduced transporter expression in the aged brain but the ability of imipramine to inhibit synaptosomal [3H]serotonin uptake was unimpaired. These effects were unique to aged animals, as prior work with young adults found no effects of dexamethasone on transporter expression. In contrast to the effects in the brain, there were no differences in platelet transporter expression between young and old rats nor did dexamethasone treatment affect the values in the aged group: thus, the platelet may not reliably model these aspects of CNS function. The results suggest that there are basic biologic differences in the effects of glucocorticoids in aged vs. young brain that could contribute to lowered effectiveness to antidepressants in elderly depression; if transport capacity is already reduced by the effects of increased glucocorticoids, further inhibition of transport by antidepressants would have proportionally less impact on synaptic serotonin concentrations.

Women at risk for postpartum-onset major depression

There is considerable evidence that the childbearing years represent a time when women are highly vulnerable to developing mood disorders. Prospective, cross-sectional, and retrospective studies have demonstrated that more than 10% of new adult mothers will experience a major depressive episode during the first postpartum year. Changes in the health care delivery system will result in increased pressure on the obstetrician/gynecologist to identify and treat women with postpartum-onset depression. Despite shortcomings in the available literature, prospective studies have identified risk factors for developing postpartum depression. Furthermore, the clear overlap between the normal sequelae of childbirth and the symptoms of major depression, including alterations in sleep, energy, libido, appetite, and body weight, underscores the need to develop guidelines for early identification. We furnish a brief overview of postpartum mood disorders with a primary focus on the antenatal and postnatal risk factors for developing postpartum depression. Based on the extent literature and our clinical experience, a set of recommendations for early identification and treatment is provided.

Recent pharmacologic advances in antidepressant therapy

The serotonergic properties of newer generation antidepressants underscore the role of 5-hydroxytryptamine (5-HT, serotonin) in both the pathophysiology and the pharmacotherapy of major depression. Clinical differences between selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs) are attributed to the greater potency and selectivity for 5-HT transporter inhibition by the SSRIs and the comparatively weak interaction of the SSRIs with nonserotonin neurotransmitter receptors. The SSRIs, monoamine oxidase inhibitors (MAOIs), and TCAs share a common adaptive regulation of noradrenergic, 5-HT, and glutamate neurotransmission, suggesting possible unifying mechanisms of action underlying their antidepressant effects. In vivo neuroimaging techniques, such as positron emission tomography (PET) and single photon emission computed tomography (SPECT) have yielded a functional neuroanatomy of compromised neurocircuitry in major depression and promise to be invaluable in mapping the in vivo effects of future novel antidepressant drugs.

Is platelet imipramine binding reduced in depression? A meta-analysis

Although it has been suggested that decreased platelet imipramine binding may be a putative biological marker of depressive illness, a number of studies have not confirmed this finding, including a recent multicenter investigation by the World Health Organization (Mellerup and Langer 1990). We performed a meta-analysis of published reports on imipramine binding in groups of depressed and healthy control subjects and found that there was a highly significant decrease in Bmax (maximal binding) values in the depressed subject groups, which was even greater among those who had been free of medication for 4 weeks at the time of investigation. This finding remained highly significant even when only high affinity binding studies (Kd < 1 nmol/L) were considered, although the absolute size of this decrease was smaller.

Classifying binormal diagnostic tests using separation-asymmetry diagrams with constant-performance curves

A method is proposed for classifying diagnostic tests that have underlying binormal distributions. The method involves using the parameters that characterize these distributions as axes of a two-dimensional graph called a separation-asymmetry (S-A) diagram. Each point on an S-A diagram corresponds to a possible diagnostic test. The diagram also has superimposed on it any of three possible families of curves of constant performance: curves of constant area under the ROC graph (iso-AUR), curves of constant overlap area (iso-OA), and curves of constant maximum information (iso-MaxInfo). Thus, the performance of any test can be determined immediately by identifying the iso-performance curve of the desired type that passes through the corresponding point of the S-A diagram. The concept of "eccentric" diagnostic tests is defined and incorporated into the S-A diagrams. The classification scheme is applied to 28 diagnostic tests. Excellent agreement is found in the ranking between the iso-OA and iso-MaxInfo measures of performance, but the iso-AUR produces markedly different results. Only three of the 28 tests were found to be eccentric. Several other interesting patterns emerged.

Reduced platelet tritium-labeled imipramine binding sites in women with premenstrual syndrome

OBJECTIVE

We studied the possible role of serotonergic systems in the cause of premenstrual affective symptoms.

STUDY DESIGN

The binding of tritium-labeled imipramine to platelets is thought to parallel central nervous system binding and to indicate serotonergic activity. We measured platelet tritium-labeled imipramine binding sites in the follicular and luteal phases in 12 controls and in 9 women with well-documented late luteal phase dysphoric disorder. In statistical analyses we used repeated measures analysis of variance, with Student-Newman-Keuls and Duncan's one-tailed t tests, and Pearson's r.

RESULTS

The values of subjects with late luteal phase dysphoric disorder were lower than those of controls (F [1,39] = 5.13, p = 0.03). Both follicular and luteal phase level were lower in subjects with late luteal phase dysphoric disorder but reached statistical significance only in the follicular phase.

CONCLUSION

Lower platelet tritium-labeled imipramine binding in women with late luteal phase dysphoric disorder supports the hypothesis that alteration of central serotonergic systems may contribute to premenstrual dysphoric symptoms.

Platelet imipramine binding in depressed children and adolescents

Kinetic constants of platelet imipramine binding were determined in youths with major depression, and a contrast group. Subjects actively depressed (N = 10) had significantly fewer imipramine binding sites (Bmax) (877 +/- 148 fmol/mg protein) than recovering depressives (N = 12) (1220 +/- 428 fmol/mg protein) and contrasts (N = 10) (1270 +/- 230 fmol/mg protein). Affinity constants (Kd) (1.14 +/- 0.36 nM, 0.97 +/- 0.31 nM, and 1.17 +/- 0.39 nM, respectively) were similar among the groups. Actively depressed males but not females had fewer imipramine binding sites than both their sex-matched comparison groups. Although actively depressed females' Bmax was significantly lower than recovering depressed and nondepressed males, neither age, Tannner stage, nor circannual rhythms influenced Bmax, but suicidality may be associated with low Bmax. A decrease in Bmax may be a state-specific marker of major depression in boys or associated with a depressive disorder with a suicidal history.

Presence of low amounts of "neuronal" antigens in cultured human skin fibroblasts

To explore the utility of cultured skin fibroblasts in investigating diseases of the nervous system in which constituents characteristic of neurons are involved, sensitive immunochemical methods were used to test for the presence in skin fibroblasts of low amounts of proteins normally used as neuronal markers. The presence of each of the neurofilament triplet proteins and of neuron-specific enolase was demonstrated by immunoblotting and by immunocytochemistry, and of an 86-kDa synapsin-like material by immunoblotting. These observations agree with previous suggestions that readily available cultured fibroblasts may be useful in investigations of disorders in which molecules are involved which are typically associated with neurons in vivo, such as Alzheimer's disease.

Platelet [3H]-imipramine binding and leukoencephalopathy in geriatric depression

We examined the relationship between platelet [3H]-imipramine binding and leukoencephalopathy as assessed by 1.5 Tesla Magnetic Resonance Imaging (MRI) in 21 elderly depressed patients who satisfied DSM-III criteria for major depression. Both drug-free platelet [3H]-imipramine binding and brain MRI studies were obtained during the same episode of depression. Our findings show a significant inverse relationship between frequency of subcortical hyperintensity (SCH) and the number (Bmax) of platelet [3H]-imipramine binding sites. Patients with Bmax less than 850 fmol/mg protein had significantly larger SCH compared with patients with a higher Bmax. These data provide further support to the potential use of platelet [3H]-imipramine binding studies and brain MR imaging as diagnostic adjuncts in geriatric depression and suggest, moreover, that these two biological markers may be linked in geriatric patients with depression.

Decreased seasonal mesor of platelet 3H-imipramine binding in depression

Seasonal cycles of platelet 3H-imipramine binding were compared in 49 endogenous unipolar depressed patients and 20 normal volunteers. A significant sinusoidal component was detected in the Bmax of binding in both patients and controls with similar amplitudes and seasonal peaks. However, the yearly average (mesor) of the patient group was significantly lower (20.0%) than that of the normal controls. The results support earlier claims of a diminished platelet binding in endogenous depression and indicate that this decrease was still evident in the presence of a 48.2% (controls) to 65.8% (patients) seasonal variation. Control Bmax values were normally distributed about a best-fit mean (cosinor fit). In contrast, patient values appeared to be bimodally distributed with one mode that was similar to controls and one mode that was substantially lower. In general, psychiatric symptoms failed to distinguish between patients with high and low platelet binding and no correlation was found between Bmax and severity of illness (HAM-D).

Neuropeptide concentrations in the cerebrospinal fluid of depressed patients treated with electroconvulsive therapy. Corticotrophin-releasing factor, beta-endorphin and somatostatin

The CSF concentrations of CRF, somatostatin and beta-endorphin were determined in nine patients who fulfilled DSM-III criteria for major depression with psychotic features. CSF samples were obtained at baseline in the depressed state, and again after a course of ECT. Concentrations of both CRF and beta-endorphin decreased after ECT, while the concentration of somatostatin increased, although the latter difference did not attain statistical significance. The increase in CSF concentrations of CRF and beta-endorphin in depressed patients is therefore seen to be state-dependent.

Effects of chronic imipramine treatment on subclasses of platelet 3H-imipramine binding sites and plasma cortisol

A decreased density of platelet 3H-imipramine (3H-IMI) binding sites has been proposed as a putative trait marker of major depressive illness. However, subsequent studies have demonstrated that the number of such sites is increased so as to be more like normal controls upon chronic treatment with antidepressant drugs. In addition, there is some evidence to suggest that altered 3H-IMI binding may be secondary to elevated plasma cortisol levels which are common in depressed patients and which normalize with remission. The present study compares platelet 3H-imipramine binding, plasma cortisol levels, and clinical improvement of 10 endogenous depressed patients before and after 6 weeks of treatment with imipramine-HCl. Total high affinity 3H-IMI binding sites were further differentiated into two subclasses on the basis of their relative sensitivities to cyanoimipramine (CNIMI) inhibition. Treatment was associated with a significant increase (134%) in CNIMI resistant binding but a decrease (45.2%) in CNIMI sensitive binding. While the former was significantly correlated with posttreatment cortisol levels, no significant correlation was found between cortisol and CNIMI specific binding. Neither site appeared to be directly related to mood state. The significance of these findings to the evaluation of platelet binding as a trait dependent marker is discussed.

Seasonal changes in cyanoimipramine specific platelet 3H-imipramine binding in depression

Seasonal variations in cyanoimipramine (CNIMI) sensitive and CNIMI resistant subclasses of platelet 3H-imipramine (3H-IMI) binding sites were studied in depressed patients and normal volunteers. Sinusoidal rhythms of the binding of both subclasses were found in patients and controls with peak levels in mid-February. Patient values of CNIMI sensitive binding fluctuated about a yearly average that was 32% lower than the average of controls. Patient deviations from the normal pattern were apparently bimodally distributed, whereas those of controls were normally distributed. CNIMI resistant binding was also normally distributed in controls, but not in depressed patients, although patient mesor values were not lower than those of controls. Platelet binding was not correlated with the severity of illness as measured by the Hamilton Rating Scale for Depression, and individual symptoms failed to discriminate between patients with high and low Bmax values.

Platelet tritiated imipramine binding in psychiatric patients: relationship to symptoms and severity of depression

The clinical and research significance of reduced imipramine binding has remained unclear despite considerable investigation. This study used an assay of demonstrated reliability to investigate the clinical correlates of imipramine binding to platelets in 63 depressed and 33 nondepressed psychiatric patients and 40 healthy control subjects. Both patient groups had Bmax values significantly lower than those of the healthy controls. Unequivocal associations between binding parameters and individual symptoms or groups of symptoms were not established, but a negative correlation between Kd and the number of adverse life events experienced in the preceding 6 months was apparent. These findings provide no support for the view that reduced binding is a trait marker for susceptibility to depression and cast doubt on its specificity as a state marker for the syndrome of depression.