Decreased uptake of 5-hydroxytryptamine in blood platelets from patients with endogenous depression

Multifaceted Regulations of the Serotonin Transporter: Impact on Antidepressant Response

Serotonin transporter, SERT (SLC64A for solute carrier family 6, member A4), is a twelve transmembrane domain (TMDs) protein that assumes the uptake of serotonin (5-HT) through dissipation of the Na⁺ gradient established by the electrogenic pump Na/K ATPase. Abnormalities in 5-HT level and signaling have been associated with various disorders of the central nervous system (CNS) such as depression, obsessive-compulsive disorder, anxiety disorders, and autism spectrum disorder. Since the 50s, SERT has raised a lot of interest as being the target of a class of antidepressants, the Serotonin Selective Reuptake Inhibitors (SSRIs), used in clinics to combat depressive states. Because of the refractoriness of two-third of patients to SSRI treatment, a better understanding of the mechanisms regulating SERT functions is of priority. Here, we review how genetic and epigenetic regulations, post-translational modifications of SERT, and specific interactions between SERT and a set of diverse partners influence SERT expression, trafficking to and away from the plasma membrane and activity, in connection with the neuronal adaptive cell response to SSRI antidepressants.

Platelet serotonin uptake in drug-naïve depressive patients before and after treatment with citalopram

We investigated the kinetic parameters of serotonin (5-HT) uptake into platelets in a group of 26 drug-naïve patients suffering from major depression before and after 3-7 weeks of treatment with citalopram. The degree of depression was rated using the Hamilton Depression Rating Scale (HDRS). The 5-HT uptake characteristics in untreated depressive patients were not significantly different from those of normal subjects. The apparent Michaelis constant (K(M)) was significantly increased, the apparent maximal velocity (V(max)) was not different from baseline, and the uptake efficiency (V(max)/K(M)) was significantly decreased after citalopram treatment. A significantly positive correlation between K(M) and V(max) was found in all groups. There was a significantly lower V(max) and V(max)/K(M) in the female compared with the male depressed patients before citalopram treatment; a hypothesis was supported that lowered 5-HT uptake may reflect a gender-linked vulnerability to a serotonin-related depression. A significant negative correlation between 5-HT uptake efficiency and the initial HDRS score suggests that platelet 5-HT uptake can be used as a marker of effective depressive disorder pharmacotherapy. The initial severity of depression was significantly negatively correlated with V(max), which supported a hypothesis that the initial severity of depressive disorder could be related to the lower V(max).

Antidepressant-binding sites in brain and platelets

[3H]Imipramine and [3H]paroxetine label with high affinity a site associated with the serotonin transporter in brain and platelets. The maximum binding capacity (Bmax) of [3H]imipramine in platelets is reduced in untreated depressed patients, and it may represent a useful biological marker in depression. The existence of an endogenous ligand acting on the [3H]imipramine-recognition site to modulate the serotonin transporter has been proposed by several laboratories. 5-Methoxytryptoline inhibits [3H]imipramine binding and [3H]serotonin uptake in the nanomolar range. This compound has been reported to occur in the pineal gland, but probably only in trace amounts. While the physiological relevance of 5-methoxytryptoline or a close analogue remains an open question, the possibility exists that the 'endocoid' for the [3H]imipramine-recognition site plays a role in the pathogenesis of depression.

Effect of cannabinoids on platelet serotonin uptake

Serotonin is involved in many of the same processes affected by cannabinoids; therefore, we investigated in vitro and in vivo effects of these drugs on the function of serotonin transporter. The effect of Delta(9)-tetrahydrocannabinol (Delta(9)-THC), endocannabinoid anandamide and synthetic cannabinoid receptor agonist WIN 55,212-2 on platelet serotonin uptake and membrane microviscosity was examined in 19 marijuana smokers and 20 controls. (1) Serotonin uptake was inhibited at higher doses of Delta(9)-THC (IC(50) = 139 micromol/l), anandamide (IC(50) = 201 micromol/l) or WIN 55,212-2 (IC(50) = 17.4 micromol/l); the inhibition was found non-competitive. Delta(9)-THC, anandamide and WIN 55,212-2 produced different effects on the membrane microviscosity. (2) Maximal velocity of platelet serotonin uptake was significantly increased in a group of chronic marijuana smokers suffering impairment of cognitive functions when compared with controls. Opposite effect of marijuana smoking on the serotonin uptake efficiency was observed in males beside females. In summary, this study provides evidence that (1) Activity of serotonin transporter is acutely affected by cannabinoids at relatively high drug concentrations; this effect is indirect and can be partially accounted for the changes in the membrane microviscosity. (2) Increase of maximal velocity of the serotonin uptake could be understood as adaptation change in the serotonergic system induced by chronic cannabis use. A hypothesis was supported that lowered serotonin uptake may reflect a gender-related differences in effects of psychoactive cannabinoids.

Serotonin transport kinetics correlated between human platelets and brain synaptosomes

RATIONALE

Blood platelets have been used extensively as a model system for investigating the role of the serotonin transporter (SERT) in various psychiatric disorders, especially depression. However, to date, it is not known whether platelet serotonin (5-HT) transport would be related to that in brain.

OBJECTIVES

We examined 5-HT transport kinetics simultaneously in human blood platelets and human cortical brain synaptosomes to determine whether they were correlated.

METHODS

Blood platelets and synaptosomes were obtained from 25 patients undergoing epileptic surgery. Synaptosomes were obtained from normal margins of surgical neuropathology specimens of anterotemporal cortex.

RESULTS

Platelet SERT V(max) was significantly correlated with brain SERT V(max) on linear regression (r=0.58, p<0.005), after controlling for the confounding effects of gender (t=-2.4, p=0.025) and time of day (t=2.1, p<0.05). Consistent with previous observations, there was a negative correlation between the maximum velocity (V(max)) of platelet 5-HT transport and pO2 (r=-0.52, p<0.01). Females had a significantly higher pO2 than males (F=4.9, p<0.05). After accounting for gender differences, addition of pO2 did not add further strength to the regression, given the aforementioned gender differences in pO2. The correlation between unadjusted values for platelet vs brain SERT V(max) was r=0.3, p=0.06.

CONCLUSIONS

These results suggest that a relationship may exist between 5-HT transport in platelets and cortical synaptosomes, when appropriate controls for confounding factors are employed.

Initial conditions of psychotropic drug response: studies of serotonin transporter long promoter region (5-HTTLPR), serotonin transporter efficiency, cytokine and kinase gene expression relevant to depression and antidepressant outcome

The Hypothesis of Initial Conditions posits that differences in psychotropic drug response result from individual differences in receptor site kinetics, and differences in the sensitivity of downstream receptor-linked responses. This work examines data consistent with the hypothesis, specific to genetic and kinetic differences of the serotonin (5-HT) transporter (SERT), as they may be linked to divergent antidepressant response (ADR). The mechanisms for divergent ADR in association with different initial SERT function are considered within the context of SERT trafficking as sensitive to various different kinase and cytokine signals, some of which are dependent on the 5-HTTLPR polymorphism of the SERT gene. Pilot data suggest that human lymphocytes show kinase changes similar to those found in rat brain with ADT. These studies additionally suggest that ADT prompts a shift in cytokine gene expression toward a greater anti-inflammatory/inflammatory ratio. These latter findings are discussed within the context of a literature suggesting increased inflammatory cytokine levels in depression, and recent observations of increased temperature associated with depression. In sum, the data suggest the opportunity to identify response dependent protein (RDP) expression patterns that may differ with dichotomous ADR, and suggest new insights into understanding the mechanisms of psychotropic drug response through an understanding of initial differences in potential for psychotropic drug target regulation during therapy.

Cholesterol-lowering therapy evokes time-limited changes in serotonergic transmission

A number of studies have reported an increased risk for violent deaths and depression in subjects with reduced serum cholesterol concentrations. Links with hypothesized impairment of serotonin neurotransmission have not been satisfactorily tested. In this investigation, the serum and membrane cholesterol, microviscosity of erythrocyte membranes, platelet serotonin uptake, and clinical parameters were determined during pharmacotherapy of 17 hypercholesterolemic patients. A significant decrease in serum cholesterol and a nonsignificant decrease in membrane cholesterol concentration were found after 2 months of simvastatin therapy. Serotonin transporter (SERT) activity was significantly increased following 1 month of simvastatin; the tendency to decrease the initial increase in SERT activity was evident following 2 months of therapy. Both membrane cholesterol and SERT activity returned to pre-treatment levels after more than 1 year of therapy. Microviscosity of plasma membranes, impulsivity, empathy, adventure, sensation seeking, and depressed mood were not markedly changed. These data indicate that long-term therapy has different effects on serotonin transmission from short-term (1- to 2-month) therapy. A significant increase in SERT activity was detected only during the first month of simvastatin therapy. This finding suggests that within this period some patients could be vulnerable to depression, violence, or suicide.

Platelet-5HT uptake and gastrointestinal symptoms in patients suffering from major depression

The objective of this study was to determine whether the presence of gastrointestinal symptoms, as defined by item 12 of Hamilton-Rating-Scale for Depression, is related to kinetic characteristics of platelet-5HT uptake in patients with major depression. The clinical picture of depression in patients with severe form of appetite loss with difficulties of eating (item 12 = 2) and weight loss was characterized by the combination of depressed mood with somatic symptoms of anxiety, sleep disturbances, decreased activity and the presence of nausea. The high frequency of relatively low Vmax and Km of 5HT uptake in this group (n = 12), all in the lower range of controls, resulted in significantly lower mean values compared with patients without gastrointestinal symptoms (n = 16; item 12 = 0) or 57 healthy subjects (Vmax = 1.36 +/- 0.27 vs. 2.14 +/- 0.85 vs. 2.05 +/- 0.74 nMol 5HT/10(9)plat.x min; Km = 382 +/- 68 vs. 467 +/- 94 vs. 492 +/- 123 nM respectively). Although our finding needs confirmation, it seems that in the research for serotonergic mechanisms in major depression, it makes sense to look at depressed patients with or without somatic symptoms separately. Based on findings in 5HT transporter knock-out mice (J. Neurosci. 15 (2001) 6348), we assume that the low apparent Vmax of platelet-5HT uptake reflects the low expression of 5HT transporter not only in platelets, but also in the gut mucosa and enteric serotonergic neurons, which probably increases the risk of typical gastrointestinal symptoms such as appetite loss and nausea occurring in some depressed patients.

Prolactin response to fenfluramine administration in patients with unipolar and bipolar depression and healthy controls

The hormonal response to the serotonin releasing agent/uptake inhibitor fenfluramine has been used as an indicator of central serotonin system function. The serotonergic system plays an important role in the etiology and pathogenesis of mood disorders. We compared the prolactin response to fenfluramine administration in unipolar depressed patients (major depressive disorder), depressed patients with bipolar disorder, and healthy controls. We found a trend towards a blunted prolactin response in depressed patients compared to healthy controls, after controlling for sex, family history, family history-by-gender interaction, and baseline levels. There was no significant difference between unipolar and bipolar patients in the baseline prolactin levels or the response to the fenfluramine administration. We also found a negative correlation between aggression and impulsivity scores and prolactin responses in subgroup with unipolar but not bipolar depression. Female patients with unipolar depression who had first-degree relatives with unipolar depression and normal controls had significantly higher prolactin responses than female patients with unipolar depression who did not have first-degree relatives with unipolar depression. The lack of difference in the response to fenfluramine administration between unipolar and bipolar depressed patients may indicate that overall serotonergic function in unipolar and bipolar depressed patients is similarly impaired.

Initial platelet serotonin (5-HT) transport kinetics predict nortriptyline treatment outcome

According to the hypothesis of initial conditions, drug response may be determined by different initial states of neurotransmitter protein recognition systems. Platelet serotonin (5-HT) transport kinetics were studied as initial-conditions predictors of antidepressant response in 24 depressed patients before and after 3 weeks of treatment with nortriptyline (75 mg). The initial affinity of the 5-HT transporter (5-HTT) correctly predicted 71% of the outcome. The pretreatment affinity constant ( Km) correlated (r = 0.61; p < 0.002) with that measured after 3 weeks of treatment (Kapp). Responding patients had a significantly higher initial Km before treatment and a significantly higher Kapp after treatment. Nonresponders had an initial Km significantly lower than that of 24 controls. Nortriptyline plasma levels were not statistically different between response groups. These results are consistent with two previously published observations, which indicate that the initial affinity of the 5-HTT predicted response to fluvoxamine or fluoxetine in the same way. Insofar as all three drugs increase the apparent affinity of the 5-HTT, it appears that a better response is related to those cases where the initial affinity is already higher before treatment.

Sertraline pharmacokinetics and dynamics in adolescents

OBJECTIVE

To determine the pharmacokinetics of sertraline in adolescents and assess its effect on a surrogate marker of serotonin transport.

METHOD

Pharmacokinetic parameters of a single 50-mg dose of sertraline were determined in 10 adolescents. Steady-state withdrawal kinetics were determined in 12 adolescents taking 50 mg/day and in 6 adolescents taking 100 to 150 mg/day. Platelet serotonin reuptake was measured before and after 2 weeks of daily 50-mg dosing.

RESULTS

The mean steady-state half-life of 50 mg was significantly shorter (15.3 +/- 3.5 hours) than the single-dose half-life (26.7 +/- 5.2 hours; t = 6.4, p < .001) and the steady-state half-life at 100 to 150 mg/day (20.4 +/- 3.4 hours; t = 2.9, p = .01). Platelet serotonin reuptake was inhibited by 61 +/- 15% after approximately 2 weeks of sertraline 50 mg/day.

CONCLUSIONS

The half-life of sertraline 50 mg becomes significantly shorter from the initial dose to steady-state, and many adolescents may benefit from twice-per-day dosing. The steady-state half-life increases as the dose increases. The moderate levels of platelet reuptake inhibition at 50 mg/day indicate that most adolescents may need sertraline doses higher than 50 mg/day to attain a therapeutic response.

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.

Serotonergic function in major depression and effect of sertraline and paroxetine treatment

We investigated platelet [14C]serotonin (5-HT) uptake and lysergic acid diethylamide [N-methyl-3H] ([3H]LSD)- and phenyl-6'-paroxetine ([3H]paroxetine) binding in 30 patients with major depression at baseline and after 6 months of treatment with either paroxetine or sertraline. The study was of a double-blind design. Baseline data was compared with an age- and gender-matched group of healthy volunteers. Baseline Vmax was significantly lower in patients than in controls. Bmax for [3H]paroxetine binding were similar in patients and controls, but patients who suffered their first depression had significantly lower Bmax for [3H]paroxetine binding than patients who had suffered multiple depressions. Twenty-three patients (76%) (13 in the paroxetine group and 10 in the sertraline group) responded to treatment as judged by a 50% or more reduction in Montgomery-Asberg Depression Rating Scale (MADRS) scores after 6 months of treatment. There were no significant differences between the paroxetine and sertraline treated groups. Both paroxetine and sertraline caused a significant reduction in Vmax and a significant increase in Km. There was a strong correlation between Km and plasma drug concentration in patients who experienced their first depression but not in patients who had suffered multiple episodes. Bmax for [3H]paroxetine binding increased after paroxetine treatment while the opposite occurred after sertraline treatment. There was a significant interaction between the impact of drug and earlier depressions. All patients included in the study had been drug free for at least 2 months. Earlier antidepressant treatment may have long withstanding effects on the serotonin uptake machinery but it cannot be excluded that the sensitivity of the uptake mechanism may become more resistant to change in patients with recurrent depressive episodes.

Decreased reuptake of serotonin in human platelets after surgery

We have documented earlier a decrease in platelet serotonin and a concurrent increase in plasma serotonin, 5-hydroxytryptamin (5-HT) after various forms of stress, suggesting a disturbed platelet 5-HT reuptake mechanism following stress. In order to further elucidate these findings, we have studied platelet 5-HT reuptake kinetics (Vmax and Km) in nine patients before and 4 days after major, uncomplicated abdominal surgery. We found a significant decrease in the maximal 5-HT reuptake velocity (Vmax) after surgery and changes in Km, verifying alterations in the affinity of the platelet 5-HT transport system. The present results thus confirm the hypothesis that 5-HT reuptake kinetics are altered following adrenergic hyperactivity. A decrease in platelet 5-HT reuptake may bear implications for our understanding of poststress adaptive changes in the cardiovascular system as well as in the central nervous system (CNS) serotonergic neurones following stressful stimulation.

A double-blind, placebo-controlled, efficacy, safety, and pharmacokinetic study of INN 00835, a novel antidepressant peptide, in the treatment of major depression

BACKGROUND

INN 00835 is a synthetic pentapeptide with a potential for rapid onset of action as an antidepressant. Its efficacy was investigated in a pilot study in patients diagnosed with major depression.

METHODS

Fifty two patients received either active drug - INN 00835 (26 patients) - or placebo (26 patients), subcutaneously at 0.2 mg/kg for 5 consecutive days. The patients were evaluated for an additional 4 weeks after treatment. Efficacy was evaluated by the following psychiatric rating scales: HAMD, MADRS, CSRS, CGI, and VAS. The effect of treatment was also evaluated by using a biochemical marker: changes in blood platelet serotonin (5HT) uptake rates in drug-treated patients compared to those in the placebo group. Plasma concentrations of INN 00835 were measured by LC/MS.

RESULTS

Statistical analysis indicated a strong pharmacodynamic correlation between plasma drug concentrations at 1 h after dosing and the reduction in the severity of depression as measured by the psychiatric rating scales. A minimum effective plasma concentration (MEC) of INN 00835 was 5 ng/ml. Statistically significant differences in response to treatment (P<0.05) were found between patients with plasma concentrations above MEC and those in the placebo group, as well as between subjects with plasma concentrations above and below the MEC. The peak effect was observed after the 5-day treatment and the response to treatment persisted during the 4-week follow-up period. The change of 5HT uptake rates after treatment was significantly larger in the drug-treated group than in the placebo group.

LIMITATIONS

This was a pilot study conducted in a relatively small population (52 patients) and the limited number of blood sampling times did not allow a comprehensive pharmacokinetic analysis. There was a relatively large placebo response. The results have to be confirmed in future, large scale studies.

CONCLUSIONS

INN 00835 appears to be a promising drug for the treatment of major depression.

5-HT1A and beyond: the role of serotonin and its receptors in depression and the antidepressant response

Since its discovery 50 years ago, the role of the indoleamine 5-HT (5-hydroxytryptamine; serotonin) in the pathogenesis of depression and in the mechanism of action of antidepressant drugs has been the subject of considerable research. Advances in molecular biology and radioligand techniques have led to the functional characterisation of at least 14 serotonin receptor subtypes. This classification has led to the development of selective compounds that have aided in the efforts of dissecting the complex role of 5-HT in depression and in mediating the antidepressant response. This review focuses largely on novel strategies of targeting specific 5-HT receptors subtypes, especially the presynaptic 5-HT(1A) and 5-HT(1B/1D) receptors. These subtypes are of primary importance in that they control the firing of the 5-HT neuron and the release of 5-HT. In addition, a number of postsynaptic 5-HT receptors have been shown to be dysfunctional in depression and are also potential targets for a number of antidepressants. We conclude that selective targeting of 5-HT receptors may lead to a faster acting and more efficient antidepressant response. Copyright 2000 John Wiley & Sons, Ltd.

Modified structure of the human serotonin transporter promoter

Recently, several studies have reported an association between anxiety traits, affective disorders and autism and alleles of a functional promoter polymorphism (5HTT-LPR) in the human serotonin transporter (5HTT, SERT).1-3 The mechanistic basis for allelic differences in transporter transcription are presently unknown. To explore this issue, we cloned the human 5HTT promoter region from a PAC genomic library and now describe an unreported 381-bp insert between the polymorphic region and the transcription start site. We verified the presence of this novel sequence by Southern hybridization of genomic digests and PCR amplifications from multiple unrelated individuals. Sequence analysis of the novel region reveals a number of canonical transcription factor binding sites (eg AP1, Elk1, NFkappaB) that may be important in controlling the response of the 5HTT gene to regulatory factors. PCR studies of genomic templates reveal a low level of amplification of a deleted template matching the size of the originally reported 5HTT promoter. This deleted template is absent from PAC amplifications, suggesting that the human 5HTT promoter may exhibit in vivo instability. Molecular Psychiatry (2000) 5, 110-115.

The effect of treatment with a new antidepressant, INN 00835, on platelet serotonin uptake in depressed patients

BACKGROUND

INN 00835 (4-fluoro-L-phenylalanyl-trans-4-hydroxy-L-prolyl-L-arginyl-glycyl-trypt ophanamide ditrifluoroacetate) is a synthetic pentapeptide antidepressant with a potential for rapid onset of action. We were interested to see if such action could be correlated with serotonin uptake by platelets.

METHODS

In a phase II clinical trial, unipolar depressed patients were administered active drug, INN 00835 or placebo, subcutaneously, at 0.2 mg/kg, once daily for 5 consecutive days. Efficacy of treatment was evaluated by psychometric tests (HAMD, MADS, CSRS, CGI and total VAS). Changes in platelet uptake rates of serotonin (3H-5HT) were measured in plasma from the patients participating in the phase II clinical trial, prior to and immediately after treatment with INN 00835 (19 patients) or placebo (16 patients), to evaluate the effect of treatment with INN 00835 on the rate of platelet 5-HT uptake.

RESULTS

The data evaluated by using the psychometric tests indicated a significant response to treatment with INN 00835 after 5 days of dosing. The rates of platelet 5-HT uptake were lower prior to treatment (baseline), and increased after the 5-day treatment period. The change in the uptake rate (deltaVmax) following treatment was significantly larger in the active group than in the placebo group (P < 0.05). The difference between the placebo group and the patients who responded to treatment was even larger.

LIMITATIONS

Small number of subjects.

CONCLUSION

The data tend to substantiate the use of platelet serotonin uptake as a biochemical marker of effective treatment of depression.

Pretreatment platelet 5-HT concentration predicts the short-term response to paroxetine in major depression. Grupo de Trastornos Afectivos

BACKGROUND

A previous retrospective study revealed that a high pretreatment platelet serotonin (5-HT) concentration was associated with a low response to serotonergic antidepressants in drug-free major depressives. We have examined such a relationship in depressive patients treated with paroxetine.

METHODS

Seventy-four drug-free major depressives (DSM-IV) were admitted to the study. Clinical ratings were performed and blood was drawn prior to the initiation of treatment and after 4 weeks of paroxetine (20 mg/day). The concentrations of 5-HT, 5-hydroxyindoleacetic acid, and tryptophan were determined in plasma and blood.

RESULTS

Paroxetine treatment reduced platelet 5-HT to 17% of baseline after 4 weeks of treatment. Responder patients had a pretreatment platelet 5-HT concentration 22% lower than nonresponders (p < .035). Admission HAMD scores, plasma paroxetine concentration, or platelet 5-HT concentration at endpoint did not differ between responders and nonresponders. Yet, the response rate was 11% in patients with high pretreatment platelet 5-HT (> 900 ng/10(9) platelets) and 50% in those below that value (p < .004).

CONCLUSIONS

These findings support that depressed patients with a high pretreatment platelet 5-HT concentration have a poor therapeutic outcome after treatment with a standard paroxetine dose. These differences may be related to the existence of molecular differences in the 5-HT transporter.

Platelet serotonin functions in untreated major depression

The uptake of [14C]5-HT, [3H]paroxetine and [3H]LSD binding was determined in platelets from 30 untreated patients with major depression and compared with corresponding variables from 30 healthy age-, sex- and season-matched control subjects. The maximum velocity (Vmax) for the 5-HT uptake was significantly decreased in patients (P = 0.014) compared to control subjects. Depressed women had significantly lower Vmax than female control subjects. In men, Vmax did not differ between patients and control subjects. Vmax was significantly lower in male inpatients compared with male outpatients (P = 0.05). The density (Bmax) of 5-HT uptake sites was found to be significantly increased in patients (P < 0.05) compared to control subjects and male patients had significantly higher Bmax than male control subjects, but there was no difference between female control subjects and female patients. No significant difference was found in Bmax of 5-HT2-receptors between patients and control subjects. A positive correlation was found between Bmax of 5-HT2-uptake sites and the degree of anxiety and between Bmax of 5-HT2 receptors and MADRS scores. Bmax of 5-HT2-receptors was positively correlated with the degree of suicidality. The results in the present study indicate that there may be a gender difference in serotonergic dysfunction in depression.

Functional polymorphism in the serotonin transporter promoter at the SLC6A4 locus and mood disorders

BACKGROUND

Heils et al found a functional polymorphism in the transcriptional control region upstream of the serotonin transporter gene at the SLC6A4 locus. The transcriptional promoter activity of the short (s) form was less than twice that of the long (l) form of the serotonin transporter promoter gene. In addition, they found individuals with the s form with associated neurotic characteristics (e.g., anxiety, anger, hostility, and depression). The purpose of this study was to determine whether or not there is an association between this functional polymorphism and mood disorders.

METHODS

The l/s polymorphism was studied in 80 patients with mood disorders and 92 control subjects.

RESULTS

There was statistically no difference between mood disorders and healthy controls in either the genotype or the allele frequency. There was statistically no difference between the genotype and subdiagnosis, family history, single/recurrent episodes of depressive disorders, suicide attempts, or the mean age of onset.

CONCLUSIONS

Our results suggest there is no association between the l/s polymorphism of the serotonin transporter gene and mood disorders.

Relationship between blood serotonergic variables, melancholic traits, and response to antidepressant treatments

The relationship between peripheral serotonergic variables, melancholic traits, and clinical improvement after antidepressant treatment was examined in 83 drug-free major depressive patients. Plasma serotonin (5-HT) concentrations was lower in untreated melancholic patients (1.00 +/- 0.11 vs. 1.84 +/- 0.28 ng/mL, p < 0.008; N = 40 and 43, respectively). A tendency was observed for plasma 5-hydroxyindoleacetic acid (p < 0.06), whereas platelet 5-HT and plasma tryptophan did not differ between groups. After blood sampling and clinical ratings, treatment began with fixed doses of 5-HT uptake inhibitors (clomipramine or fluvoxamine), monoamine oxidase inhibitors, or tianeptine, a 5-HT uptake enhancer. There was no significant difference in response rates between patients with and without melancholic traits. The relationship between the clinical response at 6 weeks (>50% reduction of baseline Hamilton score) and the pretreatment values of biochemical variables was examined. Responders had a lower pretreatment platelet 5-HT (530 +/- 36 vs. 664 +/- 50 ng/10(9) platelets, p < 0.03; N = 44 and 39, respectively). Patients with a platelet 5-HT concentration above 800 ng/10(9) platelets had a lower response rate than those below this value (p < 0.003). This difference was maximal in the subgroup of patients treated with 5-HT uptake inhibitors (N = 49). In this subgroup, the response rates of patients with 5-HT concentrations below and above the cutoff point were, respectively, 70% and 17% (p < 0.001). A pretreatment platelet 5-HT value above 800 ng/10(9) platelets had a predictive value for a negative response of 92%. These results suggest the presence of biochemical differences in the peripheral serotonergic system between melancholic and nonmelancholic patients. The inverse relationship between the pretreatment platelet 5-HT content and clinical response may be useful in the investigation of the relationship between the 5-HT system and antidepressant response.

From synapse to vesicle: the reuptake and storage of biogenic amine neurotransmitters

Biogenic amine transport systems in the presynaptic plasma membrane and the synaptic vesicle provide a mechanism for rapidly terminating the action of released transmitters and for recycling neurotransmitters. Alterations in the activity of these transporters, either by endogenous regulatory mechanisms or by drugs, affect the regulation of synaptic transmitter levels. For drugs such as antidepressants and stimulants that interact with these transport systems, the therapeutic and behavioral consequences are profound. Now that the cDNAs encoding the transporters have been isolated, we can expect rapid progress in understanding how the individual proteins work at the molecular level to couple ion gradients to the reuptake and storage of biogenic amine neurotransmitters.

Platelet-rich plasma serotonin levels in tension-type headache and depression

We measured platelet-rich plasma (PRP) serotonin in patients suffering from tension-type headache, before and after treatment with amitriptyline, comparing them with a healthy control group and patients with untreated depression. We evaluated the severity of headache and depression in each group. PRP serotonin levels were higher in patients with headache than in controls and depressed patients. We observed a fall of PRP serotonin in patients with tension-type headache to similar levels after treatment as the depressed group. This fall was correlated with the improvement of headache but not with depression scales. Our data suggest that the rise of platelet serotonin levels in tension-type headache is related to pain and not depression.

Migraine and depression: biological aspects

There is a considerable overlap in migraine and depression incidence, and both conditions may be associated with low levels of 5-hydroxytryptamine (5-HT). During a migraine attack there is evidence for low levels of platelet 5-HT and possibly also low Vmax for 5-HT uptake; both these findings are also associated with the depressed state. Both conditions can be treated by tricyclic and monoamine oxidase inhibiting antidepressants. However, there are also clear differences: migraine attacks are brief and self limiting. Part of the migraine cascade occurs outside the blood brain barrier, presumably involving blood vessels and, unlike depression, migraine attacks can be ameliorated by drugs which only act peripherally. In addition, migraine patients, especially males, often have permanently low levels of platelet monoamine oxidase activity, whereas patients with unipolar depression tend to have raised levels of this marker. This low enzyme activity may reflect part of the vulnerability to migraine, often associated in the prodromal phase with agitation or hyperactivity. Migraine may form part of a family of brief recurrent self-limiting disorders, which involve disturbances of both mood and monoamines; during the headache phase of the attack, the links with depression are most apparent.

Serotonin uptake inhibition by the monoamine oxidase inhibitor brofaromine

The selective, reversible monoamine oxidase (MAO) A inhibitor brofaromine inhibits serotonin (5-HT) uptake in animal models in vitro and in vivo. We investigated whether such an effect can be demonstrated at clinical doses in humans by treating three groups of six volunteers with either placebo, 15 mg phenelzine three times a day, or 75 mg brofaromine twice a day in a 2-week experiment. As an indirect, although relevant parameter, binding of 3H-paroxetine to the 5-HT uptake sites on blood platelets was assessed. Moreover, whole-blood 5-HT as a measure of platelet 5-HT, and serum homovanillic acid (HVA) to tentatively estimate MAO inhibition, were determined. Brofaromine reduced 3H-paroxetine binding to platelets compared with placebo by 20%-25% throughout the treatment period, significance being reached on the last treatment day. In contrast, phenelzine tended to increase 3H-paroxetine binding. Both drugs increased whole-blood 5-HT to approximately 140%-150%. Brofaromine moderately and on some days significantly decreased serum HVA, whereas phenelzine only tended to do so. Our results suggest that brofaromine at the clinically used dosage of 150 mg/day does indeed inhibit 5-HT uptake, as evidenced by measurements of 3H-paroxetine binding to platelets.

Newer aspects of the reversible inhibitor of MAO-A and serotonin reuptake, brofaromine

1. The reasons for developing second-generation MAOI are outlined. The expected advantage of reversibility as a safety valve with respect to tyramine potentiation is discussed. 2. Earlier data from in vitro and some ex vivo experiments had suggested an irreversible interaction of brofaromine with MAO-A, whereas the short duration of action, the absence of cumulation of effect and the displaceability by endogenously released substrates indicated reversibility. This apparent conflict could be solved by the demonstration that brofaromine behaves as a tight-binding reversible inhibitor. 3. In in vivo binding experiments with [3H]brofaromine given i.v., clorgyline, brofaromine and moclobemide were shown to dose-dependently displace the radioligand from MAO-A in the rat brain when administered after it. In corresponding experiments in the rat intestine in which the radioligand was administered p.o., similar results were obtained. Moreover, tyramine given orally in pressor doses after the radioligand also displaced it, confirming the idea that reversibility could act as a safety valve. 4. The evidence from animal and human experiments is presented that brofaromine is safer than classical MAO inhibitors with respect to tyramine potentiation. 5. Based on computer simulations, it is suggested that reduced liability of the new MAO reversible inhibitors to cause tyramine potentiation may potentially be linked to a reduced therapeutic efficacy. 6. The evidence is discussed that 5-HT uptake inhibition by brofaromine is relevant in its therapeutic effect in humans and may synergize with MAO-A inhibition, thus enhancing the impact of the latter on serotonergic transmission.

Platelet serotonin uptake in patients suffering from pancreatic carcinoma, chronic physical disease and depression

Serotonin uptake by platelets was determined in 11 patients suffering from carcinoma of the pancreas, eleven patients hospitalized for chronic physical disease, 19 patients suffering from major depression unipolar type, and 19 healthy volunteers. The Vmax values of serotonin uptake were significantly lower in patients suffering from carcinoma of the pancreas (F = 18.6, df = 28, Ρ < 0.001) and chronic physical disease (F = 21.3, df = 28, Ρ < 0.0001) than in healthy volunteers. The Vmax values of the depressed patients were also significantly lower (F = 4.27, df = 36, Ρ < 0.05) than those in the control group. No difference was found between the carcinomatous and the chronically ill patients. Km values of serotonin uptake by platelets were significantly decreased in both groups of patients with organic disease (F = 5.91, df = 28, Ρ < 0.025; F = 4.44, df = 28, Ρ < 0.045 respectively) as compared to the control group, but were similar in the depressed and the control groups (F = 0.42, df = 20, P = 0.52). Since the patients with chronic disease were chronically medicated, the decreased serotonin uptake may not be disease-dependent but rather associated with medication. However, the carcinomatous patients were drug-free and in this group the decreased uptake and serotonin transporter hypersensitivity may have been disease-dependent. These results suggest the involvement of the presynaptic serotonergic system in the susceptibility of pancreatic carcinomatous patients to prodromal depression.

Effect of physical stress on 5-hydroxytryptamine uptake kinetics (Km and Vmax) in human platelets

Platelet 5-HT uptake is possibly one mechanism by which plasma level of 5-HT is physiologically controlled. This mechanism may be of importance in the vascular 5-HT mediated tone and protect against thrombolysis and cardiovascular events. Physical stress is known to affect various platelet functions. The aim of this study was to investigate whether or not physical stress has any influence on platelet 5-HT uptake kinetics. In healthy adult persons (n = 13) the maximal rate (Vmax) and Michaelis-Menten constant (Km) of platelet 5-HT uptake (in vitro) were determined before (a), immediately after (b) and 1 hour after 50 min of squash playing (c). Immediately after squash Vmax and Km were elevates significantly as compared to the values before squash [Vmax(a): 77.0 +/- 31.0 (SD) pmol 5-HT/10(8) pl./min, Vmax(b): 109.9 +/- 48.4 (SD) pmol 5-HT/10(8) pl./min, p less than 0.01; Km(a): 5.16 +/- 1.73 (SD) x 10(-7) mol/1, Km(b): 7.59 +/- 2.37 (SD) x 10(-7) mol/1, p less than 0.05]. The percent elevations of Vmax (47%) and Km (42%) were of the same range. One hour after squash the values of Vmax(c) and Km(c) were found to be normalized. It is concluded that physical stress, like squash playing, does not affect net platelet 5-HT uptake in healthy persons at physiological plasma 5-HT concentrations. The significant increases of Vmax and Km of platelet 5-HT uptake are suggested to be adaptation reactions to keep the platelet net 5-HT uptake constant.

Differential regulation of the imipramine-sensitive serotonin transporter by cAMP in human JAr choriocarcinoma cells, rat PC12 pheochromocytoma cells, and C33-14-B1 transgenic mouse fibroblast cells

The imipramine-sensitive serotonin transporter appears to be the receptor for clinically important antidepressants. Some studies suggest that this protein may fall under the influence of abnormal and as yet uncharacterized regulatory effects during depressive illness. Despite these putative disease-related effects, regulation has never been demonstrated in either the platelet or synaptosome model systems. Here we demonstrate for the first time that the imipramine-sensitive serotonin transport activity in either JAr choriocarcinoma or PC12 pheochromocytoma cell lines is subject to regulation by cAMP. Unexpectedly, the regulatory effect is opposite in the two cases, causing stimulation in JAr (increased Vmax) and inhibition in PC12 (kinetically complex). Appearance of these kinetic effects lagged 15 to 20 hours behind peak cAMP levels. The results are consistent with the interesting possibility that different tissues may express isoforms of the recently cloned serotonin transporter cDNAs. We suggest, therefore, that JAr and PC12 are attractive models in which to pursue detailed analysis of serotonin transport and its manner of regulation by cAMP.

Factors influencing platelet serotonin uptake in essential hypertension

In a study of the mechanism(s) of platelet serotonin uptake alteration in essential hypertension, a total of 90 blood samples were analysed for platelet count and platelet serotonin uptake. These included 20 blood samples each of hypertensives, controls before and after cross-incubation experiments and 10 samples of hypertensives after control of blood pressure. It was observed that serotonin uptake was markedly reduced in hypertensive platelets. Diminished serotonin uptake in essential hypertension correlated directly with diastolic and mean arterial blood pressure and inversely with plasma total cholesterol values. In cross-incubation experiments using control platelets and hypertensive plasma, there was a significant reduction in platelet serotonin uptake (303.06 +/- 86.28 cpm/10(8) vs. 204.26 +/- 66.45 cpm/10(8); P less than 0.001), whereas hypertensive platelets when incubated with control plasma, showed increased serotonin uptake (233.50 +/- 75.19 cpm/10(8) vs. 312.64 +/- 79.54 cpm/10(8); P less than 0.01). Upon control of blood pressure, the platelet serotonin uptake improved significantly (205.45 +/- 70.0 cpm/10(8) vs. 266.77 +/- 61.68 cpm/10(8); P less than 0.05-0.01). From these results, it appears that reduced platelet serotonin uptake in essential hypertension is a reversible phenomenon probably governed by the presence of plasma factor(s) and/or altered platelet-membrane function.

Serotonergic function and late luteal phase dysphoric disorder

Thirty-eight subjects who met criteria for the DSM-III-R diagnosis late luteal phase dysphoric disorder (LLPDD) were compared with 18 controls in 5-HT uptake kinetics of the platelets in the premenstrual (day 26) as well as in the postmenstrual phase (day 4) of the cycle. Furthermore, 5-hydroxytryptophan (5-HTP) was administered to LLPDD patients and controls in both phases of the cycle, to investigate pituitary sensitivity for serotonin. Plasma samples for the measurement of cortisol and beta-endorphin were taken before and after oral administration of 200 mg 5-HTP, and considered as an index of pituitary-adrenal function. LLPDD was not associated with a lower platelet 5-HT uptake and content in the premenstrual phase of the cycle, compared with the postmenstrual phase. Patients appeared not to be different from controls in 5-HT uptake kinetics of platelets in the premenstrual phase of the cycle. No main differences were observed between LLPDD patients and controls in their ability to respond with secretion of cortisol and beta-endorphin to 5-HTP stimulation, either in the premenstrual, or in the postmenstrual phase. This observation could not be attributed to differences in 5-HTP metabolism. The findings of the present study do not support a specific role for 5-HT in the pathophysiology LLPDD.

Tryptophan and neutral amino acids in premenstrual syndrome

An abnormality of the serotonin system may play a role in the genesis of the symptoms of premenstrual syndrome, especially those related to mood and appetite. Whole blood and platelet uptake of serotonin are decreased during the luteal phase in women with premenstrual syndrome. The ratio of L-tryptophan (the amino acid precursor of serotonin) to the sum of the other neutral amino acids that compete for the same protein carrier cerebral uptake mechanism has been suggested to reflect central L-tryptophan levels and resultant serotonin levels in the brain. We evaluated the ratio of plasma L-tryptophan to the sum of five competing neutral amino acids in women with premenstrual syndrome and in controls. There were no significant differences between groups or across time, suggesting that it is unlikely that the aberrations of the serotonergic system in women with premenstrual syndrome are due to saturation of the tryptophan-carrying protein.

Effect of antidepressant treatment on platelet 5-HT content and relation to therapeutic outcome in unipolar depressive patients

Platelet 5-HT levels and scores on the 17-item Hamilton Rating Scale for Depression (HRS) were studied in patients with unipolar depression before and after antidepressant treatment. Before treatment there were no differences in platelet 5-HT values or in HRS scores between patients who showed a good and a poor therapeutic response. Repeated administration of 5-HT uptake inhibitors (amitriptyline, clovoxamine, fluvoxamine) for 28 days markedly decreased platelet 5-HT levels. Chronic treatment with trazodone or maprotiline (weak inhibitors of platelet 5-HT uptake) produced no changes in platelet 5-HT levels. No significant correlation was observed between platelet 5-HT concentrations and the HRS scores before or during treatment. The findings suggest that the changes in platelet 5-HT levels after antidepressant treatment are mainly due to the effects of antidepressants on the 5-HT uptake system.

Serotonin uptake and imipramine binding in the blood platelets of obsessive-compulsive disorder patients

14C-Serotonin (5-HT) uptake and 3H-imipramine binding (IB) were studied in the blood platelets of 20 obsessive-compulsive disorder (OCD) patients, 53 normal controls (5-HT uptake) and 32 normal controls (IB binding). The maximum number of binding sites (Bmax) was significantly decreased in OCD patients compared to normal controls, but there was no difference in the affinity for 3H-imipramine (Kd). The affinity for 5-HT uptake (Km) was also decreased in the OCD patients but the maximum velocity of 5-HT uptake sites (Vmax) was not significantly different in OCD patients and normal volunteers. There were trends for the Slowness Subscale of the Maudsley Obsessional-Compulsive Inventory (MOCI) to be positively correlated with the Km of 5-HT uptake (p = 0.094), whereas the Global Scale, Checking Subscale, and Doubting Conscientiousness Subscale of MOCI were negatively correlated with the Kd of IB (p = 0.066, p = 0.08, and p = 0.062, respectively). The results provide further evidence for the dysfunction of the serotonergic system in OCD.

Eating disorders and depression: is there a serotonin connection?

Central serotonin pathways modulate eating patterns, and may also participate in the regulation of behavioral impulsivity and mood. Recent studies lend support to the hypothesis that impaired postingestive satiety in bulimia nervosa is associated with reduced hypothalamic serotonergic responsiveness. Serotonin dysregulation has been implicated in major depression, and may play a role in the increased prevalence of depressive episodes in patients with eating disorders. This review compares evidence for alterations in central serotonin regulation in patients with anorexia nervosa, bulimia nervosa, and depression. It is proposed that impaired synaptic transmission in functionally distinct serotonin pathways may result in concurrent or sequential periods of binge eating, behavioral impulsivity, and depression in patients with eating disorders.

Brain 5-HT uptake sites, labelled with [3H]paroxetine, in antidepressant-free depressed suicides

Brain serotonin (5-HT) uptake sites were quantitated, by saturation binding of [3H]paroxetine, in 10 brain regions from 22 suicide victims and 20 control subjects. Suicide victims were restricted to those subjects in whom a firm retrospective diagnosis of depression was established and who had not recently been prescribed antidepressant drugs. The Kd and Bmax of [3H]paroxetine did not differ significantly between controls and depressed suicides in any of the brain regions. In putamen, Bmax values of suicides who died non-violently were lower than controls, whereas those who died by violent methods did not differ from controls. No significant differences between violent or non-violent suicides and their matched controls were found in other brain areas. These results offer little support for the view that suicide/depression is associated with an abnormality in 5-HT uptake.

Stimulation of the active transport of serotonin into human platelets by hydrogen peroxide

The effect of H2O2 on the active transport of serotonin (5-HT) by human platelets was investigated. Platelets were exposed to either a single dose of H2O2 or to H2O2 generated by the glucose/glucose oxidase or xanthine/xanthine oxidase enzyme systems. H2O2 (12.5 to 100 microM) produced a rapid, concentration-dependent and time-dependent increase in 5-HT transport which was maximal after a 2-min incubation and decreased with continued incubation. Catalase (1000 units) completely prevented H2O2-induced stimulation, and fluoxetine (1 microM) totally blocked 5-HT uptake into stimulated platelets. The glucose/glucose oxidase (3.12 to 100 milliunits) and the xanthine/xanthine oxidase system, superoxide dismutase (250 units) failed to alter the stimulation, whereas catalase (1000 units) effectively prevented the response. The kinetics of 5-HT transport indicated that H2O2 treatment did not alter the Km of 5-HT transport (Km control = 1.0 +/- 0.2 x 10(-6) M vs Km H2O2 = 1.1 +/- 0.1 x 10(-6) M) but markedly increased the maximal rate of 5-HT transport (Vmax control = 131.4 +/- 4.6 pmol/10(8) platelets/4 min vs Vmax H2O2 = 206.7 +/- 9.1 pmol/10(8) platelets/4 min). These data demonstrated that exposure of human platelets to H2O2 resulted in a stimulation of the active transport of 5-HT and suggested that H2O2 may function to regulate this process.

Changes in platelet 5-hydroxytryptamine uptake in mania

[3H]5-Hydroxytryptamine (5HT) platelet uptake was examined in a small group of hospitalised drug-free manic patients and in a larger group of drug-treated manic and schizophrenic patients compared to controls. 5HT platelet uptake was significantly higher in the manic group at the beginning of the illness episode than in either schizophrenics or controls. No difference was found in the uptake rates between the schizophrenics and controls. At discharge, manic patients had 5HT uptake values similar to control subjects. Manic patients with no previous history of either mania or depression had highly significant increases in 5HT platelet uptake compared to either schizophrenics, controls or manic patients with a previous history of manic-depression. No correlation was found between the initial increased 5HT uptake rate in the manic patient and the severity or duration of the illness episode, the length of hospitalisation or the gender of the patient.

Behavioral, neuroendocrine, and biochemical effects of 5-hydroxytryptophan administration in panic disorder

L-5-Hydroxytryptophan (5HTP) was administered to 20 patients suffering from panic disorder and to 20 healthy controls. Subjects received 60 mg 5HTP in 300 ml saline solution. Before, during, and up to 2 hours after 5HTP administration, symptoms of anxiety and depression were assessed. In addition, plasma 5HTP, 3-methoxy-4-hydroxyethylglycol (MHPG), cortisol, beta-endorphin, and melatonin levels were measured at several time points, and the kinetics of 5-hydroxytryptamine (5HT) in blood platelets were measured. During and after the infusion of 5HTP, none of the patients showed an increase in anxiety or depressive symptoms, despite the presence of severe side effects. Some patients even experienced the 5HTP infusion as a relief. In contrast to the patients, nine control subjects reported depressed mood, although no increases in anxiety were noted. In both patients and controls, the 5HTP infusion led to substantial increases in plasma cortisol and beta-endorphin levels, while the plasma MHPG level was unchanged. Plasma melatonin increased significantly after 5HTP administration, suggesting that increasing 5HT availability in man might affect melatonin synthesis. The results of this study are at odds with the hypothesis that there is a supersensitivity of 5HT2 receptors in panic disorder.

Antidepressant-anxiolytic interactions: involvement of the benzodiazepine-GABA and serotonin systems

1. Recent studies have demonstrated that antidepressant drugs are actually more effective than BZ's in the treatment of anxiety states. The role of two major neurochemical substrates that may be implicated in the anxiolytic activity of antidepressants, the benzodiazepine (BZ)-GABA receptor chloride ionophore complex and central serotonergic pathways, are focused on in this review. 2. A wide range of antidepressants elicit a reduction in BZ receptors and display anxiolytic effects within a conflict paradigm. 3. The anxiolytic activity of antidepressants, however, does not appear to be mediated via the BZ receptor, but possibly via another component of the complex such as the chloride channel-associated with the GABAA receptor. 4. Additionally, as possible candidates for the mechanism of anxiolytic activity of these compounds, results of pharmacological, behavioral and clinical studies point to the importance of serotonin (5-HT)1A receptors and 5-HT transporter sites as targets for the action of antidepressants, triazolobenzodiazepines and anxioselective piperazine derivatives.

Effects of psychotropic drugs on the behavior and neurochemistry of olfactory bulbectomized rats

Since its first characterization as a model for the detection of antidepressant drugs (van Riezen et al., 1976) a large body of data now supports the view that olfactory bulbectomy produces changes in animal behavior that are reversed by chronic treatment with antidepressants. The behavioral deficits seen in olfactory bulbectomized rats (such as irritability, deficits in acquisition of avoidance and of appetitive motivated conditioning and hyperactivity in a new environment) are probably the results of a reduced ability to adapt to environmental changes. These behavioral changes, their biochemical consequences and the effects of treatments with psychotropic drugs are reviewed. These studies suggest that the olfactory bulbectomized rat is a model of depression useful to detect antidepressant drugs.

Brain 5-HT1 binding sites in depressed suicides

5-HT1 and 5-HT1A binding sites were measured in brain tissue obtained at postmortem from 19 suicides, with definite evidence of depression, and 19 sex and age-matched controls. Thirteen of the depressed suicides had not been prescribed psychoactive drugs recently (drug-free suicides); six had been receiving antidepressant drugs, alone or in combination with other drugs (antidepressant-treated suicides). No significant differences were found in the number or affinity of 5-HT1 and 5-HT1A binding sites in frontal or temporal cortex between drug-free suicides and controls. The number of 5-HT1 sites was significantly lower (by 20%), affinity unaltered, in hippocampus and the affinity significantly lower (by 33%), number unaltered, in amygdala of drug-free suicides than controls. The number of 5-HT1 binding sites tended to be higher and the affinity lower in the antidepressant-treated compared to drug-free suicides, and significantly so in hippocampus. The present results, together with our previous studies, provide no evidence of altered cortical 5-HT markers in depressed suicides, but further emphasise abnormalities in the hippocampus.