Parameters of the potential changes induced by cevadine on striated frog muscle membrane
Dankó, M.; Cseri, J.; Varga, E.
Acta Physiologica Academiae Scientiarum Hungaricae 58(2): 103-118
1981
ISSN/ISBN: 0001-6756 PMID: 6978594 Document Number: 178879
The parameters of the potential changes induced by cevadine on striated frog muscle membrane were studied by continuous intracellular recording. The 1st response to cevadine treatment on the aneural muscle membrane was a slow depolarization of the membrane which emerged from the resting membrane potential to .apprx. -40 mV. By increasing cevadine concentration, the duration of this depolarization, called prepotential, decreased and its steepness increased simultaneously. When the slow depolarization reached the critical potential at .apprx. -40 mV a spike-like fast potential change developed. Its rate of rise was 58 .+-. 8 V/s and its overshoot + 19 .+-. 8 mV. This spike-like fast potential preceded the membrane potential oscillation without any exception and was termed starting impulse. The repolarizing phase of this wave was not complete. Three afterpotentials could be observed consistently between the starting impulse and the 1st wave of the membrane potential oscillation. The 1st one lasted for a period in the millisecond range, the 2nd one for seconds, while the 3rd afterpotential took minutes. The observed potential changes could be the result of the modification of the Na channels. The characteristic parameters of the membrane potential oscillation were determined; the rate of rise of the ascending phase and the duration of the wave were different from the corresponding parameters of the starting impulse by several orders of magnitudes. Spike-like trains were observed on that part of the muscle which was incubated in cevadine-free Ringer when the propagation of the cevadine-induced oscillation waves from the aneural part was followed. By increasing the H+ concentration, the frequency of the membrane potential oscillation was decreased, probably because of the increase of the duration of the resting period and the prepotential.