CHRONOTROPIC AND PRESSOR RESPONSES TO ANGIOTENSIN IN RATS ANAESTHETISED WITH URETHANE

Angiotensin (80 ng, i.v.) administered to ganglion-blocked rats induced and chronotropic responses the time courses of which were unrelated. Since pretreatment with bretylium or morphine reduced the chronotropic response but not the pressor response it is concluded that the chronotropic action contributes little to the pressor actions of angiotensin and is mediated via adrenergic nerves activated at morphine sensitive ganglionic sites. Comparison of the relative pressor potencies of angiotensin and vasopressin in normal, ganglion-blocked or pithed rats and in ganglion-blocked rats pretreated with atropine, morphine, bretylium, phentolamine, propranolol or adrenalectomy revealed that the pressor action of angiotensin is mainly direct in origin though a slight adrenal component is involved. © 1968.