Figure 2.

Multiple conductances underlie the NA-induced response. Voltage ramps (from -120 to -40 mV) were applied to cholinergic interneurons before and during the peak effect produced by NA application (100 μm). A, NA-induced inward current in a voltage-clamped interneuron (holding potential -60 mV). The deflections represent the voltage ramps applied before, during the maximal effect of NA, and after drug washout. B, Representative example of a recording in which the estimated reversal potential was close to -120 mV (a). In another set of recordings the apparent reversal potential was close to -40 mV (b). In the remaining cells, the current—voltage relation did not appear to cross in the voltage range tested or at more positive or negative values (c). The traces shown on the right represent the net NA current recorded at different voltage values obtained by digital subtractions for the corresponding I–V curves shown on the left. C, Changes in extracellular potassium concentration modify the amplitude of the NA-induced current in a dose-dependent manner.