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

The effects of nitric oxide (NO) synthase inhibitors on the electrical ly evoked release of [H-3]acetylcholine were studied in guinea-pig mye nteric plexus preparations preincubated with [H-3]choline. N-G-monomet hyl-L-arginine (EC(50) 5.3 mu mol 1(-1)) and NG-nitro-L-arginine (EC(5 0) 1.3 mu mol 1(-1)) concentration-dependently increased the evoked re lease of [H-3]acetylcholine without affecting the basal outflow The fa cilitatory effect of N-G-monomethyl-L-arginine was prevented by L-argi nine but not by D-arginine. The results suggest that endogenous NO inh ibits the depolarisation-evoked release of acetylcholine.