Circannual variations in the binding of [3H]lysergic acid diethylamide to serotonin2A receptors and of [3H]paroxetine to serotonin uptake sites in platelets from healthy volunteers

Background: Circannual variations occur in several serotonergic parameters, including platelet serotonin uptake and platelet [H-3]imipramine binding. Methods: Binding of [H-3]lysergic acid diethylamide ([H-3]LSD) to platelet serotonin (5-HT)(2A) receptors and binding of [H-3]paroxetine to platelet serotonin uptake sites were studied longitudinally for 1 year in 12 healthy volunteers. Results: For [H-3]LSD, the number of binding sites (B-max) showed no significant seasonal variation (two-way analysis of variance), although B-max was significantly higher during the months October through February than during the months April through August (32.6 vs. 29.8 fmol/mg protein; p = .015). For [H-3]paroxetine, B-max showed a significant seasonal variation (p = .003) with maximum in August (1322 fmol/mg protein) and minimum in February (1168 fmol/mg protein). The affinity constant (K-d) showed a significant seasonal variation for [H-3]LSD binding (p = .046), but not for [H-3]paroxetine binding. The seasonal fluctuations in [H-3]LSD binding and in paroxetine binding tended to be inversely correlated for B-max (r = -.70; p = .08) and were significantly negatively correlated for (r = -.88; P = .009). Conclusions: The present study demonstrates a seasonal effect on platelet serotonin uptake site binding and indicates a possible seasonal effect on 5-HT2A receptor binding. The results imply that circannual fluctuations should be taken into account when these platelet serotonin markers are studied (C) 1998 Society of Biological Psychiatry.