[Potential-dependent ion currents in the membrane of the striated muscle of the lamprey].

Membrane ionic currents were recorded in thin striated muscle bundles of lamprey suction apparatus by means of double sucrose gap method. In response to depolarization fast inward Na+ and delayed outward K+ currents appeared with steady-state characteristics similar to that in frog muscle membrane. The only difference consisted in lower steepness of the inactivation curve for K+ current. This probably suggests a greater density of slow potassium channels. The presence of two fractions in potassium current is suggested from changes both in reversal potential and in speed of the current deactivation during long lasting depolarizing pulses. No functioning voltage-dependent calcium channels were detected in the lamprey muscle membrane.