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. 1998 Feb 15;18(4):1449–1464. doi: 10.1523/JNEUROSCI.18-04-01449.1998

Fig. 3.

Fig. 3.

Whole-cell patch-clamp recordings of the inward and outward currents. Current traces are shown at the same scale, whereas the time base was varied, as indicated in the calibration bars.A1, A2, Current traces (bottom traces) from accommodating (A1) and silent principal cells (A2) elicited by 5 mV (20 msec) voltage steps from −35 to −20 mV (top traces), performed in control ACSF. B, Current traces in accommodating principal cell (bottom traces) elicited by 10 mV (80 msec) voltage steps from −130 mV to 0 voltage (top traces in inset), performed in ACSF containing 1 μm TTX. Inset, Current–voltage curve of peak current in accommodating principal cells, measured between 3 and 6 msec after onset of voltage steps in control ACSF (•) (n = 4) and in the presence of 1 μmTTX (○) (n = 4). There was a significant difference (p < 0.05) in outward current amplitude from −30 to 0 mV before and after TTX application. This suggests the presence of a Na-dependent outward current. All of the subsequent recordings were performed in the presence of TTX.C, Current traces (bottom traces) elicited by using 600 msec voltage steps from −60 to −10 mV, with 10 mV increments preceded by a 200 msec prestep to −120 mV (top traces). Transient and sustained components can be observed in the current traces in addition to spontaneous EPSCs inC–E. C–E are shown at the same time base. D, Current traces (bottom traces) elicited by using 600 msec voltage steps from −60 to −10 mV, with 10 mV increments. The steps are preceded by a 200 msec prestep to −40 mV (top traces). The transient current was inactivated entirely by the prestep. E, Transient current obtained by subtraction of D from C.F, Instantaneous current–voltage curve (•) obtained by extrapolating the tail current at the onset of the testing voltage step, and the steady-state current–voltage curve (○) obtained by measuring the current amplitude at the end of testing voltage steps. The intersection of the two curves indicates the reversal potential at −75 mV (−78 mV after adjustment of the liquid junction potential). Inset, Reversal of the tail currents with voltage (bottom traces). The total current was activated by a 6 msec voltage step to +20 mV, which was preceded by a 200 msec prestep to −120 mV (top traces). Reversal of the tail currents was analyzed by using 50 msec test potentials from −60 to −130 mV, with 10 mV increments.