NG-nitro-L-arginine methyl ester-induced norepinephrine release from cardiac sympathetic nerve endings in anesthetized cats.

ABSTRACT

Using the cardiac dialysis technique in the anesthetized cat, we examined the effects of NG-nitro-L-arginine methyl ester (L-NAME, a nitric oxide (NO) synthase inhibitor, 100 mM) on sympathetic modulation. Local administration of L-NAME induced increases in dialysate norepinephrine (NE) levels, which were not affected by the addition of omega-conotoxinGVIA. High-potassium (high K+)-evoked increases in dialysate NE levels were suppressed by addition of L-NAME. To confirm the involvement of NO in the NE releasing action, we compared dialysate NE levels during the administration of L-NAME or D-NAME and no significant differences between them. L-NAME induces spontaneous non-exocytotic NE release but suppresses exocytotic NE release by high K+. L-NAME may interact with both NE transport and NE release mechanisms. However, NO may contribute little to the amounts of NE released by L-NAME.