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Science 1 April 1966:
Vol. 152. no. 3718, pp. 97 - 99
DOI: 10.1126/science.152.3718.97
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Articles

Tetrodotoxin and Manganese Ions: Effects on Electrical Activity and Tension in Taenia Coli of Guinea Pig

Y. Nonomura 1, Y. Hotta 1, and H. Ohashi 1

1 Department of Pharmacology, Faculty of Medicine, University of Tokyo, Tokyo, Japan

Tetrodotoxin, at concentrations up to 5 x 10-6 gram per milliliter, has no effect on the spontaneous discharge in the smooth muscle of taenia coli. However, the spontaneous discharge is abolished by Mn++ at a concentration of 0.5 millimole per liter. The contraction induced by immersing the muscle in isotonic KCl solution is also suppressed in the presence of Mn++. Because Mn++ is a specific suppressor of the spike induced by Ca++ and tetrodotoxin is an inhibitor of the spike induced by Na+, we suggest that Ca++ is a charge carrier in the production of spike potential in the smooth muscle and that the entry of intervening Ca++ through the membrane acts as a trigger for the contraction of smooth muscle.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Effects of Tetrodotoxin on Excitability of Squid Giant Axons in Sodium-Free Media.
A. Watanabe, I. Tasaki, I. Singer, and L. Lerman (1967)
Science 155, 95-97
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Science. ISSN 0036-8075 (print), 1095-9203 (online)