1) Properties of the slow potential changes recorded from antral and pyloric regions of the guinea pig stomach were investigated with both the double sucrose gap and microelectrode methods. 2) Frequency, amplitude, and duration of the slow potential changes varied from 2 to 5 per min, 0 to 30 mV, and 6 to 14 sec. 3) During the slow potentials, membrane resistance was reduced. This reduction exceeded that caused by the rectifying property of the membrane. 4) The amplitude of the slow potential was enhanced by application of weak inward current pulses and decreased during weak outward current pulses. 5) The frequency of the slow potential changes was a function of the temperature. The Q10 value was 3.2. 6) Na-deficient (1/10 Na) Krebs solution suppressed the slow potential changes, but they were restored by conditioning hyperpolarization of the membrane. However, in Na-free solution the slow potential changes were generated with neither normal nor hyperpolarized membrane. 7) In low K-and low Ca-Krebs solutions, the amplitude and frequency of the slow potential changes were reduced. 8) When Cl ion was replaced by the less permeable C5H5SO3 ion, the slow potential change was abolished completely. When. Cl ion was substituted with Br ion, the frequency of the slow potential was not reduced, and in some preparations it was increased. 9) Ba ion in the presence of Ca ion increased the frequency of the slow potential changes, but in the absence of Ca ion the frequency was not increased. Sr ion could not be substituted for Ca ion in the generation of the slow potential changes.

SummaryElectrical and mechanical properties of M. digastricus of the guinea pig were investigated by the microelectrode and strain gauge methods.