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

Abstract

Background: Seasonal affective disorder (SAD) has been regarded as a melatonin disorder, but the pathophysiological mechanisms of SAD are to a large extent unclarified. Serotonergic mechanisms have also been studied, but they have shown inconsistent results. Methods: We have compared [ 3H]paroxetine and [ 3H]lysergic acid diethylamide (LSD) binding in platelets from 23 SAD patients and 23 controls. Then SAD patients had 4 weeks of light therapy. On the last treatment day new blood samples were drawn. Symptoms before and after light treatment were measured by SIGH-SAD. Results: B max for paroxetine binding before light treatment was higher in SAD patients compared to controls and also higher in responders than in nonresponders. B max decreased significantly during light treatment. We also found a negative correlation between the two B max values before but not after light treatment. There was a negative correlation between B max for paroxetine binding before treatment and clinical status after treatment. Patients with reduced B max for LSD binding after treatment had a better clinical treatment response. Conclusions: The present study indicates that serotonin receptor parameters might be suitable in the prediction of clinical response to light treatment.