The effects of synthetic alpha-human atrial natriuretic peptide (alpha-hANP) on the overall baroreflex system in anesthetized mongrel dogs.

The effects of alpha-hANP (0.3 micrograms/kg body weight/min) on the baroreflex system were studied in anesthetized dogs according to three different protocols. In the first protocol, the effects of alpha-hANP on an open-loop gain (G(AP)) of the overall baroreflex system and a gain (GHR) of the baroreflex heart rate control system during quick mild hemorrhage and blood infusion were studied. G(AP) was decreased from 7.6 +/- 0.6 to 2.8 +/- 0.5 by alpha-hANP with hemorrhage. G(AP) decreased 7.4 +/- 0.8 to 2.9 +/- 0.4 by alpha-hANP with blood infusion. G(AP) was restored nearly to the control levels one hour after alpha-hANP administration. GHR did not change by alpha-hANP administration. In the second and third protocol, a site of action of alpha-hANP was analysed. alpha-hANP inhibited the responses of systemic vascular resistance to quick mild hemorrhage and blood infusion, but did not affect the responses of cardiac output to quick mild hemorrhage and blood infusion in the second protocol. After carotid sinus denervation and vagotomy, alpha-hANP inhibited an arterial pressure responses to phenylephrine and nitroglycerin bolus injection in the third protocol. These findings suggest that alpha-hANP has mainly an effect on the peripheral vascular system to decrease its responsiveness, resulting in a decrease in G(AP).