Fig. 7.

Effect of 5-methylfurmethiodide (MFI) on depolarization-activated potassium currents in n-methyl-d-glucamine (NMDG) Ringer solution. A) Ramp currents from the experiment shown in Fig. 6B. Note that there is a reduction from 58 Nan amps (nA) to 46 nA in the current step associated with the voltage step −15 to −35 mV indicating that 100 µM MFI limits opening of voltage-activated currents at depolarized potentials. B) The muscle cell was held at −35 mV and rectangular depolarizing steps were made to different potentials in 5 mV steps to activate the potential dependent potassium channels. The control currents reduced in the presence of 100 µM MFI and increased again on wash. C) Peak outward current-voltage plots: control (●) and in the presence of 100 µM MFI (○). The plots are fitted with the Boltzmann equation (equation-1) to obtain estimates of the constants (see Table 1). MFI inhibits the outward current by reducing the maximum current and decreasing the half-activation potential.