FURTHER CHARACTERIZATION OF THE INHIBITION OF PLATELET-AGGREGATION BYA PLASMA FACTOR(S) IN UNMEDICATED UNIPOLAR DEPRESSED-PATIENTS

To investigate further the inhibition of platelet aggregation by a pla sma factor(s) in unipolar depression, a series of assays were performe d in which the platelet-rich plasma of a male volunteer was preincubat ed with the plasma of either unmedicated unipolar depressed patients o r age- matched controls. Platelet aggregation was initiated by the fol lowing aggregating agents; ADP (10 and 2.5 mu-M), ADP/5HT (0.5 mu-M AD P+50 mu-M 5HT and 0.5 mu-M ADP+25 mu-M 5HT) and adrenaline (10 and 1 m u-M) (that act on different platelet membrane receptors) and by the fo llowing agents; sodium fluoride (20 mM), calcium ionophore A23,187 (19 mu-M) and phorbol-12-myristate-13-acetate (3.24 mu-M) (that act at sp ecific intracellular sites). The plasma of depressed patients signific antly reduced the platelet aggregatory response for each of the aggreg ating agents at each of the concentrations tested. Therefore, it is co ncluded that the inhibition of platelet aggregation by a plasma factor (s) may be irreversible in nature and may have an intracellular site(s ) of action, possibly at, or beyond, the site of activated protein kin ase C.