Seasonal changes in cyanoimipramine specific platelet 3H-imipramine binding in depression.

Seasonal variations in cyanoimipramine (CNIMI) sensitive and CNIMI resistant subclasses of platelet 3H-imipramine (3H-IMI) binding sites were studied in depressed patients and normal volunteers. Sinusoidal rhythms of the binding of both subclasses were found in patients and controls with peak levels in mid-February. Patient values of CNIMI sensitive binding fluctuated about a yearly average that was 32% lower than the average of controls. Patient deviations from the normal pattern were apparently bimodally distributed, whereas those of controls were normally distributed. CNIMI resistant binding was also normally distributed in controls, but not in depressed patients, although patient mesor values were not lower than those of controls. Platelet binding was not correlated with the severity of illness as measured by the Hamilton Rating Scale for Depression, and individual symptoms failed to discriminate between patients with high and low Bmax values.