Fig. 6. Calcium currents and corresponding current–voltage relationships in muscle fibres from honeybee. (A) Inward calcium currents were evoked with 100 ms long depolarizing pulses in a voltage-clamped single fibre in the presence of potassium channel blockers, from a holding potential of –80 mV. Open circle, peak of the current; closed circle, end of the depolarization pulse. (B) Mean membrane–current relationship established at the peak of the current (open circles, N=14) and at the end of the depolarization pulses (closed circles). The mean curves were separately fitted using Eqn 1 (see Materials and methods) with values of G_max, V_rev, V_0.5 and k of 210 S/F, +45 mV, –10.9 mV and 5.6 mV (upper panel) and 267 S/F, +32 mV, –10 mV and 6 mV (lower panel). E_m, voltage command.