KINETIC SEPARATION OF CHARGE MOVEMENT COMPONENTS IN INTACT FROG SKELETAL-MUSCLE

1. Procedures for a complete charge movement separation employed a com bination of its steady-state inactivation and activation properties in intact frog skeletal muscle fibres in gluconate-containing solutions. 2. Holding potential shifts from -70 to -50 mV reduced the total char ge available between -90 and -20 mV from 16.76 +/- 1.70 nC mu F-1 (mea n +/- S.E.M.; n = 4 fibres) to 9.25 +/- 1.43 nC mu F-1 without signifi cant loss of tetracaine-resistant charge (q(beta)). 3. The steady-stat e and kinetic properties of tetracaine-sensitive charge (q(gamma)) per sisted through holding potential changes from -90 to -70 mV in the pre sence of gluconate and generally resembled activation properties estab lished hitherto in sulphate-containing solutions. 4. Further holding p otential displacement to -50 mV abolished q(gamma) charge movements an d depressed the charge-voltage curve. 5. Test voltage steps applied fr om a -70 mV prepulse level gave rapid monotonic g(beta) decays and sim ilarly depressed activation functions in 2 mM tetracaine unchanged by holding potential shifts between -70 and -50 mV. 6. The isolated 'on' q(gamma) charge movements, I(t), always included early transients that preceded any prolonged charging phases and which increased with depol arization. They decayed to stable baselines in the absence of prolonge d time-dependent or inward-current phases and yielded integrals, Q(t), that monotonically increased with test voltage. 7. 'Off' steps always elicited rapid monotonic q(gamma) decays that fully returned the 'on' charge. 8. 'On' and 'off' q(gamma) currents, I(t), following voltage steps from fixed conditioning to varying test levels mapped onto topol ogically distinct higher-order phase-plane trajectories, I(Q), that st eeply varied with test Voltage. 9. In contrast, voltage steps to fixed test potentials of either -70 or -20 mV elicited identical q(gamma) p hase-plane trajectories independent of prepulse history. 10. The q(gam ma) current thus reflects an independent, capacitative process driven uniquely by higher-order dependences upon charge distribution, Q(t), a nd test voltage, V(t), autonomous of prepulse history or time, t.