Two-component slow waves in smooth muscle of cat stomach

Abstract

Cat stomach in vitro shows spontaneous activity of slow waves and spikes; the slow waves consist of an initial rapid component which is Na dependent, is propagated and not correlated with contractions; and a 2nd slow component which is Ca dependent, is abolished by Mn++, may not be propagated but is always found when contractions occur. Spikes may appear on the 2nd component and enhance contractions. Both components of slow waves originate in longitudinal muscle. Ouabain reduces the 1st wave, initially stimulates spiking and later reduces frequency of the 2nd wave. Tetrodotoxin has no apparent effect on either slow-wave component. Frequency of spontaneous waves is reduced by low Cao and enhanced by high Ca0 but this effect of Ca0 requires the presence of Na. The 1st component is analogous to the slow waves of small intestine, the 2nd to pre-potentials and spikes of taenia coli.