Response of the Hemostatic System to Acute Vital Stress in Rats.

We studied the effect of acute vital stress on the parameters of the hemostasis system in young and old Wistar rats. The psychotraumatic effect was simulated as a situation of emotional stress at the sight of a predator (Indian python) catching and eating a conspecific. In young rats, acute vital stress was followed by inhibition of platelet aggregation, hypercoagulation by the external pathway and final stages of plasma hemostasis, and a decrease in fibrinogen and antithrombin III levels against the background of fibrinolysis activation. In old animals, increased platelet count with reduced aggregation capacity, hypocoagulation by the internal pathway of the plasma hemostasis activation, signs of thrombinemia (a 2-fold increase in soluble fibrin-monomer complexes), an increase in antithrombin III, and inhibition of the fibrinolytic system were observed. Age-related changes in the hemostasis parameters in rats were determined before and after stress exposure.