Effects of Paralytic Shellfish Poison on the Movements of Excised Small Intestine of a Guinea Pig

Abstract

This study was performed in order to investigate the effects of gonyautoxins (GTXs) and tetrodotoxin (TTX) on the movement of the excised small intestine of a guinea pig.The results may be summarized as follows:1) The peristaltic movement appeared when pressure was applied to the internal wall of the excised intestinal canal by the method of Trendelenburg. However, after pretreatment of the intestine with GTXs (1.0MU/ml) for 2min, this movement was not observed.2) The tonic contractions of the intestinal preparation induced by adding acetylcholine (ACh, 1×10-7g/ml) to the organ bath were not suppressed by pretreatment with GTXs (1.0MU/ml) or TTX (1.0MU/ml) for 3min.3) The contractions induced by nicotine (1×10-5g/ml) were markedly suppressed by pretreatment with GTXs (1.0MU/ml) or TTX (1.0MU/ml) for 3min.4) The contractions of the intestinal preparation elicited by transmural electrical stimulation (0.5msec duration, 40Hz supramaximal voltage) were completely suppressed by pretreatment with GTXs (1.0MU/ml) or TTX (1.0MU/ml) for 3min.From these results, it may be concluded that GTXs have inhibitory effects on the liberation of ACh from the nerve endings, but not on the ACh receptor of the smooth muscle.