Endogenous and exogenous nitric oxide inhibits norepinephrine release from rat heart sympathetic nerves.

Abstract This study was designed to elucidate whether nitric oxide (NO) controls norepinephrine (NE) release from sympathetic nerves of the rat heart. Hearts were perfused in the Langendorff mode with Tyrode’s solution. The right sympathetic nerve was stimulated with trains of 1 or 3 Hz and NE release was measured. The NO synthase (NOS) inhibitor N G -nitro- l -arginine (L-NNA) enhanced the evoked NE release in a concentration-dependent manner. This facilitation was independent of the increase in perfusion pressure and was stereospecifically reversed by l -arginine but not d -arginine. Another NOS inhibitor, N G -methyl- l -arginine, produced a similar increase in NE release. The NO-donor …