Fig. 2.
Electrophysiological characteristics of hydroxylamine- and SNAP-induced excitation of striatal cholinergic interneurons. A, In a current-clamp experiment, hydroxylamine (100 μm) (a) and SNAP (100 μm) (b) depolarized a striatal cholinergic interneuron without affecting the apparent input resistance of the cell. To compare the effects of both compounds on this electrophysiological parameter, membrane potential value was returned to the control level by continuous injection of 100 pA negative current. Resting level was −61 mV. Downward deflections are hyperpolarizing electrotonic potentials evoked by rectangular current pulses (200 pA, 2 sec); their decline after the initial peak reflects the prominent Ih in these cells.B, In another striatal interneuron recorded in the voltage-clamp mode, 100 μm hydroxylamine produced an inward current (a). This effect persisted unchanged in the presence of 1 μm TTX, to block voltage-dependent sodium channels (b). Holding potential was −60 mV. C, Current–voltage relationship of a cholinergic interneuron before (open circles) and during 100 μm hydroxylamine (filled circles). The values were calculated by measuring the steady-state current generated by 3 sec voltage steps of progressively increasing and decreasing amplitude. Holding potential was −60 mV.