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

Y. Nonomura, Y. Hotta and H. Ohashi
Science
New Series, Vol. 152, No. 3718 (Apr. 1, 1966), pp. 97-99
Stable URL: http://www.jstor.org/stable/1718800
Page Count: 3
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Tetrodotoxin and Manganese Ions: Effects on Electrical Activity and Tension in Taenia Coli of Guinea Pig
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Abstract

Tetrodotoxin, at concentrations up to 5 $\times $ 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 Ca$^{++}$ through the membrane acts as a trigger for the contraction of smooth muscle.

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