Cardiovascular actions of angiotensin in the fowl (Gallus domesticus). I. Analysis.

Chicken aorta, unlike the aortae of any other species tested, did not respond to angiotensin II (AII) at concentrations up to 10(-4) M. The anesthetized chicken did, however, show a blood pressure increase in response to AII, but this was apparently dependent on the sympathetic nervous system. In the conscious chicken a biphasic response to AII was seen--an initial depressor response followed by a pressor response. The depressor response was not inhibited by standard blocking agents, but was blocked by prior induction of tachyphylaxis to vasopressin. It is concluded that the depressor response to AII in the conscious chicken is due to release of vasotocin, the avian equivalent to vasopressin, and the subsequent pressor response to AII is due to activation of the sympathetic nervous system.