PLATELET-AGGREGATION AND DENSE GRANULE SECRETION IN SCHIZOPHRENIA

The functional state of platelets and their possible impairment in res ponse to various stimuli were assessed in saline-diluted citrated bloo d samples of normal male central subjects (n = 27), and in schizophren ic patients with (n = 34) and without(n = 23) haloperidol treatment. I n response to collagen, but not to arachidonic acid (AA) and adenosine diphosphate, platelet aggregation (as measured by changes in impedanc e) was significantly higher in both haloperidol-treated and drug-free schizophrenic patients than in normal control subjects. Comparison of the secretion traces, however, indicated that only AA-induced adenosin e triphosphate (ATP) release was significantly lower in haloperidol-tr eated schizophrenic patients than in normal control subjects. In respo nse to thrombin, collagen, and AA, the mean values of ATP release from drug-free patients were significantly higher than those from the same individuals when they were receiving haloperidol. Furthermore, there was a trend toward increased ATP release (in response to thrombin or c ollagen) in the nonrelapsed group of drug-free schizophrenic patients as compared with the relapsed group. The collagen-induced platelet agg regation or dense granule secretion in drug-free patients was correlat ed significantly and negatively with psychosis ratings. Such changes i n platelet function of schizophrenic patients were not correlated sign ificantly with daily haloperidol dose, plasma haloperidol levels, age of subjects, age of onset, or duration of illness.