Neurohypophysial peptides and central cardiovascular control.

The cardiovascular effects of intravenous and intracisternal administration of neurohypophysial peptides were studied in anaesthetized dogs. Intracisternal oxytocin (1 and 10 mU kg-1) increased blood pressure. Intravenous lysine vasopressin (0.1 to 100 mU kg-1) induced a dose-dependent increase in blood pressure with bradycardia. Intracisternal lysine vasopressin (0.01 to 10 mU kg-1) elicited a dose-related decrease in blood pressure but no change in heart rate. These central hypotensive effects of vasopressin were suppressed by intravenous guanethidine, dl-propranolol, prazosin or atropine and were not observed in diabetes insipidus dogs with surgical lesion of the supra-opticohypophysial tract. Hypotension elicited by intracisternal vasopressin was due to a decrease in sympathetic tone and simultaneous activation of parasympathetic tone. These results suggest the involvement of these peptides in central control of blood pressure.