ROLE OF NITRIC-OXIDE IN ADRENAL CATECHOLAMINE SECRETION IN ANESTHETIZED DOGS

We examined the role of nitric oxide (NO) in adrenal catecholamine sec retion in response to splanchnic nerve stimulation (SNS) and exogenous acetylcholine (ACh) in anesthetized dogs. The NO synthase inhibitor N -omega-nitro-L-arginine methyl ester (L-NAME), NO donor -methyl-2-nitr osohydrazino)-N-methyl-1-propanamine (NOC 7), and ACh were administere d intra-arterially into the adrenal gland. The increases in catecholam ine output induced by ACh (0.75-3 mu g) were enhanced by L-NAME (0.1-1 mg/min) and inhibited by NOC 7 (0.2-2 mu g/min). Inhibition by NOC 7 (2 mu g/min) was observed during treatment with L-NAME (1 mg/min). The increases in catecholamine output induced by SNS (1-2 Hz) were inhibi ted by L-NAME and by NOC 7. No inhibitory effect of NOC 7 was observed during treatment with L-NAME. These results suggest that NO may play an inhibitory role in the regulation of adrenal catecholamine secretio n in response to exogenous ACh.