Fig. 7.

Nicotinic receptor-mediated currents measured with voltage clamp under conditions in which voltage-sensitive conductances were blocked. Pipettes contained a CsCl-based solution; the external solution contained 2 μm atropine, 0.5 μmTTX, 40 μm DNQX, 5 mm CsCl, and 200 μm CdCl₂. A, Carbachol (100 μm) increased the instantaneous current, elicited a negative shift of the holding current, and increased the membrane noise. B, The difference currents are primarily voltage- and time-insensitive. C, The I–Vrelationship of the difference current is linear over a wide range of voltage. The current amplitudes were averaged over the whole trace. The reversal potential (−17.0 mV) was calculated by the linear fit to the plot.