Abstract

Blood pressure and heart rate responses to catecholamines were observed under conditions known to reduce the differences between the autonomous equilibrium of trained and control groups. In albino rats the experiments were performed after bilateral vagotomy and in restraint stress while in humans the effect ofduodenal acidification was examined. Trained groups have never displayed reduced responses in this artificial autonomous equilibrium. No intergroup difference was found in the responses to alpha stimulation, but alpha blockade, beta stimulation and beta blockade elicited more marked reactions inthe trained groups. As shown by the results, regular physical training does notreduce the sensitivity of the adrenergic receptors. When any change occur-red at all, it suggested rather an elevated sensitivity, especially in case ofbeta receptors. The modified responses observed in vivo in the trained groups are thus due to other mechanisms, such as the mentioned offset in resting autonomous regulation of the cardiovascular functions, and not to sensitivity changes. Verf.-Referat