[Thrombocyte aggregation and the release of ATP from their dense granules in immobilized rats]

In August rats, 24-h immobilization stress (IS) decreased the rate and amplitude of platelet aggregation induced by collagen (2-4 microgram/ml) or ADR (0.25-5.0 microM) in platelet-rich plasma, but had no effect on ATP release reaction. Platelet aggregability unchanged in groups deprived of food and water for 24 h or subjected to 6-h IS. Only after 24-h IS were the effects of collagen and low concentrations of ADP potentiated by preincubation of platelets with epinephrine (1 microM). The IS-induced decrease in platelet aggregation to 2 micrograms/ml collagen correlated significantly with the thymus involution, and both effects were most pronounced in rats displaying low activity scores in a hole-board apparatus. The data strongly implicate behavioral variables in the stress-induced changes in platelet functions.