Inhibitory Effect of Tetrodotoxin on the Contractile Activity of the Guinea-pig Ileum and Distal Colon

1. Effects of tretrodotoxin, ganglion blocking drugs, cholonergic blocking drugs, adrenergic blocking drugs and junction potential blocking drugs on the contractile activity of intestine were investigated. 2. Tretradotoxin produced the distinct relaxation and inhibited the contractile activity of the guinea-pig ileum and distal colon while no inhibitation or slight increase in the contrastile activity of the guinea-pig taenia strip preparation, cat and rabibit ileum were observed. 3. Ganglion blocking drugs, hexa,ethonium, lidocaine and dibucaine, showed the inhibitory action on the guinea-pig distal colon. In constrast, potentiation in the contractile activity of the rabbit ileum was obserced except dibucaine. 4. All cholinergic blocking drugs produced the inhibitory effect on the guinea-pig distal colon. 5. No distinct change or slight increase effect of adrenergic blocking drugs were observed on the guina-pig distal colon, expect phenoxybenzamine. In rabbit ileum, the potentiation on the contractile activity was observed by adrenergic blocking drugs expect phenoxybenzamine. 6. The possibility which excitatory dominant in the intrinsic neurones of guineapig ileum and distal colon was discussed.