INCREASE BY NO SYNTHASE INHIBITORS OF ACETYLCHOLINE-RELEASE FROM GUINEA-PIG MYENTERIC PLEXUS

The effects of nitric oxide (NO) synthase inhibitors on the electrically evoked release of [H-3]acetylcholine were studied in guinea-pig myenteric plexus preparations preincubated with [H-3]choline. N-G-monomethyl-L-arginine (EC(50) 5.3 mu mol 1(-1)) and NG-nitro-L-arginine (EC(50) 1.3 mu mol 1(-1)) concentration-dependently increased the evoked release of [H-3]acetylcholine without affecting the basal outflow The facilitatory effect of N-G-monomethyl-L-arginine was prevented by L-arginine but not by D-arginine. The results suggest that endogenous NO inhibits the depolarisation-evoked release of acetylcholine.