Action of tetrodotoxin on the contractile responses of isolated guinea-pig urinary bladder preparation to x-irradiation and to electrical stimulation.

Tetrodotoxin (10- minus 8 to 10- minus 6 g/ml) blocked the contractile responses of isolated guinea-pig urinary bladder preparation to electrical (25 and 100 Hz) neural but not to transmural stimulation and to X-irradiation (50 kV, 20 kR/min, 20 kR). The irradiation had no influence on the bladder responses to electrical and hormonal (acetylcholine and histamine) stimulation. It is concluded that the X-ray-induced contraction is of myogenic origin and that it is possibly not related to the electro-mechanical coupling system.