Figure 3.

The influence of extracellular leptin on the taste cell currents in control lean (BALB) mice and diabetic (db/db) mice. (a and b) Voltage-dependent whole-cell currents evoked by depolarizing voltage steps up to +60 mV in 10-mV increments from a holding potential of −60 mV in the absence (1) and in the presence (2) of leptin in BALB mice (a) and db/db mice (b). The amplitudes of transient inward and outward currents greatly varied from cell to cell. (c) I–V curves of amplitudes of steady-state outward currents obtained from the records a and b. (d) Dose–response relationship for the increment ratio of steady-state outward currents as a function of leptin concentration. Amplitudes of steady-state outward currents induced by a voltage step from −60 mV to +40 mV were measured and the amplitudes in the absence of leptin were taken as 1.0. The error bar represents the SEM obtained from three to eight cells. (e) The whole-cell currents induced by a depolarizing ramp wave of 290 mV/s in the absence (curve 1) and in the presence (curve 2) of leptin. (Inset) I–V relation obtained by subtracting curve 1 from curve 2 demonstrating that the reversal potential of leptin-activated current was approximately −87 mV. (f) Changes in resting membrane potentials and input resistances induced by 10 ng/ml leptin measured under current clamp mode.