IONIC MECHANISM OF THE RESTING MEMBRANE DEPOLARIZATION OF FROG SARTORIUS MUSCLE INDUCED BY DIMORPHOLAMINE

Ionic mechanism of the resting membrane depolarization of frog sartorius muscle induced by dimorpholamine was studied in a variety of ionic conditions. The resting membrane was depolarized in a dose-dependent manner reaching a maximum with a dose of 6×10-5 M. The amount of the depolarization (1.4 mV) was suppressed with doses over 10-4 M. This dose-dependent response was accompanied by change in the membrane conductance. The chloride conductance was increased by 16 % and the potassium conductance by 7 %, however the sodium conductance did not significantly change with a dose of 2×10-5 M. The slight depolarization induced by the drug was well explained by the changes in the ionic conductance. The effects of these actions on the membrane action potentials were simulated, suggesting that this drug possesses the nature of a stimulant on excitable membranes, yet does not produce any appreciable depolarization blockade.