TEMPORARY INCREASE OF PLASMA EPINEPHRINE AFFECTS STRESS RESPONSES 24HLATER

The impact of temporary (24 h) implantation of epinephrine tablets on catecholamine responses to handling and immobilization 24 h later was investigated in rats. Free plasma epinephrine responded with an increa se to both types of stress (77% and 326%, respectively) while controls showed a weaker response to immobilization. The basal level of free p lasma norepinephrine was reduced (46% vs. controls) after epinephrine pretreatment, but neither handling nor immobilization had a specific e ffect on this parameter. In contrast, the basal level of free plasma d opamine was increased after epinephrine pretreatment (183%); however, as with free norepinephrine, there was no specific effect of handling or immobilization. Conjugated plasma epinephrine was significantly low ered after epinephrine pretreatment (44% vs. controls). It did not res pond specifically to handling or immobilization, except for a stronger response after 20 min of immobilization. Conjugated norepinephrine sh owed no specific response, but increased nonspecifically after extende d immobilization. Conjugated dopamine was lowered (30%-48%) in the E-t reated group and did not respond to stress at any time. Thus, a tempor ary elevation of free plasma epinephrine affected, differentially, bas al levels and stress responses of free and conjugated catecholamines 2 4 h later.