PLATELET SEROTONERGIC FUNCTIONS AND LIGHT THERAPY IN SEASONAL AFFECTIVE-DISORDER

We investigated platelet C-14-serotonin uptake and platelet [H-3]LSD a nd [H-3]paroxetine binding in 11 patients with seasonal affective diso rder (SAD). Patients were reinvestigated after light therapy, applied at 07.00-09.00 h for 10 consecutive days. The degree of depression was rated before and after light therapy using the Comprehensive Psychopa thological Rating Scale (CPRS). Baseline data in patients were compare d with data from a control group consisting of 11 age-and sex-matched healthy volunteers. Seven patients responded to light therapy with a > 50% reduction in CPRS scores. In non-responders, the reduction in CPR S was 24.7 +/- 5.5%. There was a significant inverse correlation (P=0. 014) between K-m for platelet C-14-serotonin uptake and CPRS scores. P atients had significantly higher B-max for platelet [H-3]LSD binding ( P=0.04) and significantly lower B-max for platelet [H-3]paroxetine bin ding (P=0.016). There was a strong, multiple correlation between B-max for [H-3]LSD, as the dependent variable, and K-m, V-max and B-max for [H-3]paroxetine binding in patients (P<0.0001) but not in controls. R esponders to light therapy had significantly higher K-m (P=0.023) and significantly lower B-max for [H-3]paroxetine binding (P=0.028) than n on-responders. B-max for [H-3]paroxetine binding increased significant ly to normal levels after light therapy. The results indicate that SAD is associated with aberrations in the serotonin uptake mechanism. The enhanced 5-HT2-receptor density may reflect a consequential up-regula tion. (C) 1998 Elsevier Science Ireland Ltd.