Effect of adaptation to physical exercise on α-adrenoceptor reactions of isolated resistance artery during acute experimental myocardial infarction.

The contractile reactions of the caudal artery mediated by α-adrenoceptors do not significantly differ during experimental myocardial infarction in nonadapted rats and rats adapted to graded physical exercise (swimming). In nonadapted rats, experimental myocardial infarction produces a drastic inhibition of the contractile responses in comparison with nonadapted intact rats, which is related to desensitization of α-adrenoceptors. In adapted rats the contractile reactions markedly increased during myocardial infarction due to high sensitivity and density of α-adrenoceptors. Therefore, adaptation mobilizes the reserve capacities to normalize blood pressure during experimental myocardial infarction. [ABSTRACT FROM AUTHOR]