Different reflex responses in cardiac and renal sympathetic nerve activities during coronary occlusion in the dog.

Abstract

This study was undertaken to scrutinize the difference in the response of cardiac sympathetic nerve activity (CSNA) and renal nerve activity (RNA) to coronary artery occlusion. The magnitudes and time courses of per cent changes in CSNA and RNA, recorded simultaneously in 22 dogs, were compared with each other during a 1 min occlusion of the left circumflex coronary artery under four different conditions. With afferent nerve intact, changes in CSNA and RNA showed similar biphasic patterns comprising initial increases (CSNA, 9 +/- 3.1% (S.E.); RNA, 16 +/- 6.4%, at 20 sec of occlusion) and subsequent decreases (CSNA, -3 +/- 4.3%; RNA, -11 +/- 6.5%, at 60 sec), despite the progressive fall in arterial pressure (from 109 +/- 4 to 89 +/- 4 mmHg). After carotid sinus denervation, the initial increases in both nerve activities were reduced and the subsequent decreases became more evident. The decreases in RNA (-47 +/- 8.0%) were significantly greater than those in CSNA (-23 +/- 5.6%). After bilateral cervical vagotomy, changes in both CSNA and RNA showed in contrast similar monophasic increasing patterns (CSNA, 18 +/- 4.0%; RNA, 25 +/- 5.6%, at 60 sec), where RNA increased more than did CSNA. After carotid sinus and vagoaortic denervation, CSNA and RNA increased only slightly throughout the occlusion. These results conclusively indicate that the reflex responses in CSNA and RNA during coronary occlusion are quantitatively different, though qualitatively similar, and that RNA is inhibited significantly more than CSNA by the reflex mediated through the afferent vagal nerves.