Platelet [3H]paroxetine and [3H]lysergic acid diethylamide binding in seasonal affective disorder and the effect of bright light therapy

Bright light therapy for depression: a review of its effects on chronobiology and the autonomic nervous system

Bright light therapy (BLT) is considered among the first-line treatments for seasonal affective disorder (SAD), yet a growing body of literature supports its use in other neuropsychiatric conditions including non-seasonal depression. Despite evidence of its antidepressant efficacy, clinical use of BLT remains highly variable internationally. In this article, we explore the autonomic effects of BLT and suggest that such effects may play a role in its antidepressant and chronotherapeutic properties. After providing a brief introduction on the clinical application of BLT, we review the chronobiological effects of BLT on depression and on the autonomic nervous system in depressed and non-depressed individuals with an emphasis on non-seasonal depression. Such a theory of autonomic modulation via BLT could serve to integrate aspects of recent work centered on alleviating allostatic load, the polyvagal theory, the neurovisceral integration model and emerging evidence on the roles of glutamate and gamma-hydroxybutyric acid (GABA).

Enhanced serotonin transporter function during depression in seasonal affective disorder

Decreased synaptic serotonin during depressive episodes is a central element of the monoamine hypothesis of depression. The serotonin transporter (5-HTT, SERT) is a key molecule for the control of synaptic serotonin levels. Here we aimed to detect state-related alterations in the efficiency of 5-HTT-mediated inward and outward transport in platelets of drug-free depressed patients suffering from seasonal affective disorder (SAD). 5-HTT turnover rate, a measure for the number of inward transport events per minute, and tyramine-induced, 5-HTT-mediated outward transport were assessed at baseline, after 4 weeks of bright light therapy, and in summer using a case-control design in a consecutive sample of 73 drug-free depressed patients with SAD and 70 nonseasonal healthy controls. Patients were drug-naive or medication-free for at least 6 months prior to study inclusion, females patients were studied in the follicular phase of the menstrual cycle. All participants were genotyped for a 5-HTT-promoter polymorphism (5-HTTLPR) to assess the influence of this polymorphism on 5-HTT parameters. Efficiency of 5-HTT-mediated inward (p=0.014) and outward (p=0.003) transport was enhanced in depressed patients. Both measures normalized toward control levels after therapy and in natural summer remission. Changes in outward transport showed a clear correlation with treatment response (rho=0.421, p=0.001). Changes in inward transport were mediated by changes in 5-HTT transport efficiency rather than affinity or density. 5-HTTLPR was not associated with any of the 5-HTT parameters. In sum, we conclude that the 5-HTT is in a hyperfunctional state during depression in SAD and normalizes after light therapy and in natural summer remission.

Bright light exposure during acute tryptophan depletion prevents a lowering of mood in mildly seasonal women

We investigated the influence of bright light exposure on the mood-lowering effect of acute tryptophan depletion (ATD). Mildly seasonal healthy young women without a personal or family history of psychiatric disorders remained in either dim or bright light during two test days. Tryptophan-deficient and nutritionally balanced amino acid mixtures were administered in counterbalanced order. Mood state was assessed using the Profile of Mood States (POMS) and Visual Analogue Scales (VAS). In dim light, ATD decreased POMS scores across most subscales, indicating a worsening of mood. In bright light, mood was unaffected by ATD. Thus, bright light blocked the worsening of mood caused by ATD. This was also observed on the positive mood VAS. These results indicate a direct, immediate interaction between bright light and serotonin function. Bright light might help protect against ATD-induced mood change by increasing serotonin above the threshold level below which there is a lowering of mood.

Enhancing women's mood and energy: a research-based program for subthreshold depression using light, exercise, and vitamins

The prevalence and clinical significance of subthreshold forms of depression with sequelae comparable to major depression have been recently described in the literature; however, research on effective treatment is rare. A new intervention program that combines a specific regimen of light, exercise, and vitamins is effective in improving women's mood and overall sense of well-being. This program is well suited to many patients who present with somatic and psychological symptoms consistent with subthreshold depression.

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

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

Antidepressant effects of light therapy combined with sleep deprivation are influenced by a functional polymorphism within the promoter of the serotonin transporter gene

BACKGROUND

A functional polymorphism within the promoter of the serotonin transporter has been shown to influence the antidepressant response to serotonergic drug treatments and to total sleep deprivation (TSD). The short-term relapse that follows acute response to TSD has been successfully prevented by combining TSD with light therapy. The mechanism of action of this combined treatment is unknown.

METHODS

We tested the hypothesis that allelic variation of the serotonin transporter (5-HTT) linked polymorphic region (5-HTTLPR) could influence the response to the combination of light therapy and TSD. Twenty-two bipolar depressed inpatients were administered a night of TSD combined with 30 min light therapy given during the TSD night and in the morning after recovery sleep. 5-HTTLPR was genotyped using polymerase chain reaction techniques. Changes in perceived mood were rated on a visual analog scale.

RESULTS

Light therapy sustained the effect of TSD. The effect was more marked in homozygotes for the long variant of 5-HTTLPR than in heterozygotes and homozygotes for the short variant.

CONCLUSIONS

The influence of 5-HTTLPR on response to the combination of TSD and light therapy is similar to that observed on response to TSD and serotonergic drug treatments.

Binding of [3H]paroxetine to serotonin uptake sites and of [3H]lysergic acid diethylamide to 5-HT2A receptors in platelets from women with premenstrual dysphoric disorder during gonadotropin releasing hormone treatment

Changes in serotonergic parameters have been reported in psychiatric conditions such as depression but also in the premenstrual dysphoric disorder (PMDD). In addition, hormonal effects on serotonergic activity have been established. In the present study, binding of [3H]paroxetine to platelet serotonin uptake sites and binding of [3H]lysergic acid diethylamide ([3H]LSD) to platelet serotonin (5-HT)2A receptors were studied in patients with PMDD treated with a low dose of a gonadotropin releasing hormone (GnRH) agonist (buserelin) or placebo and compared to controls. The PMDD patients were relieved of premenstrual symptoms like depression and irritability during buserelin treatment. The number of [3H]paroxetine binding sites (Bmax) were significantly higher in the follicular phase in untreated PMDD patients compared to controls. When treated with buserelin the difference disappeared. No differences in [3H]LSD binding between the three groups were shown. The present study demonstrated altered platelet [3H]paroxetine binding characteristics in women with PMDD compared to controls. Furthermore, [3H]paroxetine binding was affected by PMDD treatment with a low dose of buserelin. The results are consistent with the hypothesis that changes in serotonergic transmission could be a trait in the premenstrual dysphoric disorder.

Seasonal affective disorder and serotonin-related polymorphisms

Disturbances in central serotonergic systems have been hypothesized to be involved in seasonal affective disorder (SAD). Association between SAD and the shorter allele of the serotonin transporter promoter repeat length polymorphism (5-HTTLPR) has been reported in an American sample. We have genotyped 82 SAD patients and 82 healthy controls from Sweden, Finland, and Germany for this and five other polymorphisms in the genes coding for serotonin receptors 5-HT2A and 5-HT2C, tryptophan hydroxylase and white. No associations with SAD or seasonality (seasonal variations in mood and behavior) were detected. Although minor effects cannot be excluded, our results suggest that these polymorphisms do not play a major role in the pathogenesis of SAD in the northern European population.

Platelet serotonin transporters and the transporter gene in control subjects, unipolar patients and bipolar patients

OBJECTIVE

The purpose of the present study was to relate the number of platelet serotonin transporters in unipolar and bipolar patients and in control subjects to two polymorphisms in the serotonin transporter gene: a VNTR in intron 2 and a deletion/insertion in the promoter region.

METHOD

Density of platelet serotonin transporters was determined by radioligand binding analysis. Genotyping was performed by PCR amplification of polymorphic regions followed by size determination of the obtained fragments.

RESULTS

The control subjects and the two groups of patients were similar with respect to the genotype and allele distribution belonging to the two polymorphisms in the serotonin transporter gene for. An interaction between status (control, unipolar- or bipolar patient) and VNTR genotype regarding the number of platelet serotonin transporters was observed; unipolar patients with the genotype 12/10 had more platelet serotonin transporters than bipolar patients and controls with this genotype. No association related to the polymorphism was found in the promoter region of the serotonin transporter gene.

CONCLUSION

An association was observed between the polymorphism in intron 2 of the serotonin transporter gene and the number of platelet serotonin transporters. Unipolar patients with a particular genotype had more platelet serotonin transporters than the corresponding controls and bipolar patients.

Paroxetine binding in aggressive schizophrenic patients

Decreased central serotonergic activity has been associated with aggressive behavior in humans and animals. Whether or not this phenomenon is related to current aggression or to aggressive tendency is debatable. [3H]paroxetine binding in blood platelets represents the activity of serotonin peripheral binding sites. We investigated a possible association between [3H]paroxetine binding in blood platelets and current aggression or homicidal history in schizophrenic patients. Blood platelets of 11 aggressive schizophrenic patients were assayed for [3H]paroxetine binding in blood platelets and compared to findings in 15 non-aggressive schizophrenic patients, 15 presently non-aggressive schizophrenic patients with homicidal history, and 15 healthy volunteers. Clinical evaluation was performed using the Positive and Negative Syndrome Scale, the Hamilton Rating Scale for Depression and the Clinical Global Impression scale. B(max) of [3H]paroxetine binding in blood platelets of currently aggressive schizophrenic patients was significantly higher than that in platelets of non-aggressive schizophrenic patients, presently non-aggressive patients with homicidal history and healthy volunteers. No difference was found between the last three study groups. No significant correlation was found between scores of all rating scales and the investigated biochemical parameters. An association was found between current aggression among schizophrenic patients and high B(max) values of [3H]paroxetine binding in blood platelets. This association is probably related to present state of aggression rather than to tendency towards aggression.

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

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

Enhanced platelet serotonin 5-HT2A receptor binding in anorexia nervosa and bulimia nervosa

Some evidence exists to suggest that serotonin 5-HT2A receptor function is altered in anorexia nervosa and bulimia nervosa. In order to further investigate the 5-HT2A receptor in eating disorders, platelet [3H]lysergic acid diethylamide ([3H]LSD) binding was studied in ten patients with anorexia nervosa, 23 patients with bulimia nervosa and 33 healthy controls. At admission, Bmax for platelet [3H]LSD binding was significantly higher both in the anorexia nervosa group (30.6+/-4.2 fmol/mg protein; mean+/-S.D.) and in the bulimia nervosa group (30.8+/-7.6 fmol/mg protein) than in the control group (23.5+/-6.3 fmol/mg protein; p=0.01 and p=0.003, respectively). Kd was borderline significantly higher among anorexics (median 1.45 nM) and significantly higher among bulimics (median 1.66 nM) than among controls (median 0.95 nM; p=0.05 and 0.003, respectively). The Global Assessment of Functioning score and the body mass index were both significantly negatively correlated to Kd (r=-0.40; p=0.03 and r=-0.41 p=0.03, respectively), but not to Bmax. The present study indicates that patients with anorexia nervosa as well as patients with bulimia nervosa have an enhanced 5-HT2A receptor binding and provides further evidence for a serotonergic dysfunction in eating disorders.