Abstract
The purpose of the present study is twofold, firstly to investigate the effects of alpha-human atrial natriuretic polypeptide (α-hANP) on norepinephrine overflow from sympathetic nerve endings, and secondly to compare vascular responsiveness in perfused mesenteric preparations in spontaneously hypertensive rats (SHR, Okamoto and Aoki, 7-9 weeks old) and a cohort of Wistar Kyoto rats (WKY). In preliminary studies using normotensive Wistar rats, the pressor responses to electrical nerve stimulation or exogenous norepinephrine application were inhibited by α-hANP. Norepinephrine overflow was also suppressed by α-hANP, during nerve stimulation. The pressor responses and norepinephrine overflow during nerve stimulation were significantly greater in SHR than in WKY rats. The inhibitory effect of α-hANP on these responses was reduced in SHR. These results indicate that α-hANP could affect both pre- and post-synaptic sites of the resistance vessels. Further, the reduced inhibition of pressor responses and norepinephrine overflow by -hANP in SHR suggests an insufficient regulation of adrenergic transmission by -hANP in hypertension.
