EFFECTS OF PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE ON CARDIOVASCULAR AND RESPIRATORY RESPONSES IN ANESTHETIZED DOGS

This study examines some of the cardiovascular and respiratory effects of pituitary adenylate cyclase-activating polypeptide (PACAP) in anae sthetised dogs. Intravenous injection of PACAP 27 caused an increase i n arterial blood pressure and an increase in heart rate. The blood pre ssure response was significantly reduced by adrenoceptor blockade sugg esting a mechanism of action mediated in part via catecholamines. The heart rate increase was unaltered by adrenoceptor blockade suggesting a direct effect of PACAP 27. PACAP 27 also caused potentiation of card iac slowing caused by stimulation of the vagus nerve. In addition, PAC AP 27 powerfully stimulated breathing. This was probably evoked by sti mulation of arterial chemoreceptors, because bilateral section of the carotid sinus nerves abolished this effect. PACAP 27 had no effect on the ability of the cardiac sympathetic nerve to increase heart rate, n or on the interaction between the sympathetic and parasympathetic syst ems in the heart.