EFFECT OF VERATRINE ON MUSCLE FIBRE MEMBRANE AND ON NEGATIVE AFTER-POTENTIAL

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Abstract
The effect of veratrine on the electrical properties of frog''s sartorius muscle was investigated in the resting and active fiber using inside-the-cell microelectrode techniques. In the resting fiber treatment with veratrine sulfate concentrations of 10-8 to 2.5 x 10-7 g/cc produced an increase in the membrane capacity (Cm) and a decrease in the membrane resistance (Rm) without appreciably altering the membrane potential. Under these conditions veratrine treatment apparently produces a non-specific increase in membrane permeability. Veratrine greatly retards repolarization following the action-potential spike (the veratrine negative after-potential). The Na conductivity of the membrane was greater during the veratrine negative after-potential than in the resting fiber, and that the delay in repolarization seemed to be due to this increased Na conductivity. Reduction of the external Na concentration either greatly reduced or completely eliminated the veratrine negative after-potential.

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