Effect of atrial natriuretic factor and 8-bromo cyclic guanosine 3':5'-monophosphate on [3H]acetylcholine outflow from myenteric-plexus longitudinal muscle of the guinea pig.

摘要: We report that atrial natriuretic factor (ANF) inhibits electrically induced cholinergic twitches of longitudinal muscle in whole intestinal segments and myenteric-plexus (MPLM) strips from the guinea pig ileum. To elucidate possible presynaptic mechanism ANF's action, we studied spontaneous stimulation-evoked radiolabeled acetylcholine (ACh) outflow MPLM after incubation with [3H]choline. developed a method mounting treating preparations, which allowed us, at same time, to record isometric contractions determine [3H]ACh upon electrical stimulation by train three pulses. ANF (5 x 10(-8) M), norepinephrine (2 10(-7) M) 8-bromoguanosine 3':5'-cyclic monophosphate (10(-3) nearly equieffective concentrations caused similar inhibition twitches. However, had no effect on outflow, whereas was found suppress 3':5'-cGMP enhanced outflow. 7.0-fold increase cGMP over control values, predominantly layers, Escherichia coli heat-stable toxin (12.5 U/ml) elicited 35-fold increment extramuscular layer. Thus, is able elevate smooth inhibit MPLM. This mimicked exogenous endogenously generated cyclic nucleotides. suggest depressive action mediated via its postsynaptic impact implicating elevation muscle.