SYMPATHETIC RESPONSES IN CARDIAC TISSUE IN EXPERIMENTAL HYPERTENSION

¹ Pharmacological Evaluation Section, Wyeth Laboratories, Radnor, Pennsylvania

The function of the heart is essential hypertension and its response to sympathetic stimulation remain to be clarified. The effects of activation of the adrenergic system in isolated rat atria as well as the contractility of the tissue were examined in the present study. Contractile force exerted at various lengths and at equivalent resting tensions by preparations from hypertensive animals was either comparable to controls or only slightly reduced. Furthermore, increases in contractility initiated by paired stimulation were not significantly different in the two groups. Sympathetic activation by field stimulation and administration of tyramine caused comparable increases in contractile force in both groups, attesting to the integrity of the peripheral sympathetic nervous system. Norepinephrine also produced similar responses in both types of preparations. It is concluded that sensitivity to peripheral sympathetic activation is normal in atria derived from hypertensive animals.