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Journal of Experimental Biology 86,237-248 (1980)
Published by Company of Biologists 1980

Rhythmic Electrical Activity in Stomach and Intestine of Toad

ALLEN MANGEL 1 and C. LADD PROSSER 1

1 Department of Physiology and Biophysics, University of Illinois Urbana, Illinois 61801, U.S.A.

The intact stomach of the toad initiates rhythmic slow-spikes of 5-15 s duration and frequency of 3-5 min-1. The spontaneous electrical waves originate in the longitudinal muscle layer; isolated circular muscle is quiescent. Aboral conduction velocity is 0.12–0.9 mm s-1. Reduction of external sodium concentration from 89.5 to 15 mM produced no effect on slow spikes, although further reduction to 1.5 mM increased frequency and decreased amplitude. Slow-spikes were unaffected by ouabain or by incubation in potassium-free solution. When calcium in the medium was reduced, slow-spike amplitude and frequency decreased. Slow-spikes exhibited a change in amplitude of 16 mV per decade change in CaO2+; slow-spikes were eliminated at 10-8 M CaO2+ and by blockers of calcium conductance channels.

Intact intestine of toad demonstrated slow-waves which resembled those of mammalian intestine. These were sensitive to changes in external sodium and were eliminated by 1 x 10-4 M ouabain.

It is suggested that rhythmic slow-spikes of longitudinal smooth muscle of amphibian stomach may result from periodic changes in Ca conductance whereas endogenous electrical waves of intestine may result from rhythmic extrusion of sodium.

Submitted on August 20, 1979






© The Company of Biologists Ltd 1980