Effects of removal and reapplication of K+ and Cl- on spontaneous electrical activity, slow wave, in the circular muscle of the guinea-pig gastric antrum

In the circular muscle of guinea-pig gastric antrum, the effects of removal and reapplication of K+ and Cl- were studied on the slow wave, which consi sts of the lower, first and upper, second components. The first component a ppeared to be triggered by the driving potential generated in the interstit ial cells. K+ removal slightly depolarized the membrane, increased frequenc y, and shortened the first component and driving potential, and K+ reapplic ation hyperpolarized and prolonged these potentials transiently. Ouabain ab olished the K+-induced hyperpolarization but had no inhibitory effect on th e K+-induced potentiation. The K+-induced prolongation was much reduced in Ca2+-deficient and increased in Ca2+-excess solution. BAPTA-AM, thapsigargi n, and cyclopiazonic acid shortened the slow wave and inhibited the K+-indu ced prolongation but did not block the slow wave. Effects of Cl- removal we re stronger than K+ removal in shortening and increasing the frequency. In Cl--deficient solution, no prolongation was observed on K+ reapplication. A lthough no conclusive evidence was obtained as to the ionic mechanism invol ved in the effects of K+ or Cl- removal and reapplication, a possibility is considered that the sarcoplasmic reticulum is involved in determining the duration of the driving potential and the first component of the slow wave.