Tritiated imipramine binding sites in affective disorders and schizophrenia. Influence of circannual variation.

We have investigated platelet [3H]imipramine binding in normal controls and patients with primary endogenous depression (unipolar and bipolar) or schizophrenia. Absolute Bmax values did not differ between subgroups. However, when circannual variation of binding was taken into account by expressing results as percentages of normalised values derived from the multiple linear regression of Bmax values as a function of time of sampling, schizophrenic patients were found to have higher Bmax than normal controls. There was no significant difference between depressed patients and controls, nor between patients exhibiting plasma cortisol suppression and non-suppression after the dexamethasone suppression test. A significant negative correlation was found between relative Bmax values and cerebrospinal 5-HIAA levels in depressed patients.