Effect of restraint stress on rat brain serotonin

Restraint-induced stress in rats was found to enhance steady state concentrations of whole brain and hypothalamic serotonin, at 1,2 and 4 h after immobilization. The increase was maximal at 1 h and tended to decline thereafter. The rate of accumulation of rat brain serotonin, in pargyline pretreated animals, was significantly enhanced after restraint stress. Bilateral adrenalectomy and metyrapone, an endogenous corticoid synthesis inhibitor, failed to affect restraint stress (1h)-induced increase in rat brain serotonin levels. Thus restraint stress-induced autoanalgesia and potentiation of the pharmacological actions of several centrally acting drugs, in rats, are serotonin-mediated responses. The results also indicate that restraint stress-induced effects on rat brain serotonin are not dependent on endogenous corticoid activity.