Alteration by a plasma factor(s) of platelet aggregation in unmedicated unipolar depressed patients

To investigate whether a plasma factor(s) modulates platelet aggregation in unipolar depression, a series of assays were performed in which the platelet rich plasma of a male volunteer was preincubated with the plasma of either unmedicated unipolar depressed patients or age and sex matched controls. Platelet aggregation was initiated by the addition of a number aggregating agents (ADP, ADP/5-HT, adrenaline, noradrenaline, collagen, thrombin and ristocetin) acting on different platelet membrane receptors. The plasma of depressed patients significantly reduced the platelet aggregatory response for each of the aggregating agents used. Therefore, it is concluded that factor(s) which inhibit platelet aggregation may be present in the plasma of unmedicated unipolar depressed patients.