| Abstract: | To determine if functional cholinergic innervation occurs in the frog duodenum or not, the effects of exogenous acetylcholine and electrical transmural stimulation, the contractile activity of an acid extract from the frog duodenum, and the distribution of acetylcholinesterase (AChE) activity in the wall of the frog duodenum were investigated. Acetylcholine caused non-sustained contraction in a dose-dependent manner (100 nM-1 mM). The ED50 value was 17 +/- 2.4 microM. Atropine (500 nM) shifted the dose-response curve for acetylcholine parallel to the right. Transmural stimulation of the frog duodenum caused frequency-dependent (0.5-50 Hz) contraction which was not decreased by atropine (500 nM) at all. The acid extract from the frog duodenum caused contraction of a longitudinal muscle strip of guinea-pig ileum but atropine (500 nM) had no significant effect on the contraction. Only a little AChE activity was found in Auerbach's plexus of the frog duodenum compared with that of the rat ileum. These results suggest that a cholinergic nerve is present in the frog duodenum but its physiological significance is very small. |
