Abstract
Wick and pressure electrode recording were used to locate the sites where spontaneous activity originates in isolated bundles of the circular smooth muscle layer of frog stomach. In long bundles up to three pacemaker regions were found to be active. Electrical activity of pacemaker regions as recorded with pressure electrodes is characterized by a distinct prepotential which has not been observed to precede action potentials of other regions of the bundle. Pacemaker sites are up to 8 mm away from each other. They appear to be spatially fixed and do not shift with time. When pacemaker regions were excised, we did not observe spontaneous activity in the remaining segments. Stimuli which usually induce activity in latent pacemaker regions are ineffective in such segments. Along the circumference of intact muscle rings of the stomach also three pacemaker regions have been located. Pacamaker frequency increases in aboral direction and is one per minute in the fundus region and 6 per min in the pyloric region.
Published Version
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