Figure 3.

Low conductance end plate channels persist in AChRɛ^−/− mice. (A) Single channel currents in wild-type (wt) (Left) and AChRɛ^−/− muscle (Right) recorded from P5 (upper traces) and P30 (lower traces) end plate. Membrane potential was approximately −100 mV in each experiment. Membrane potential was estimated from current reversal potential measurement in the same patch. Temperature 20°C, inward current is downward. (B) Amplitude distribution of single channel currents recorded from the end-plate of wild-type (wt) and AChRɛ^−/− muscle at P30 as shown in A. Each histogram was fitted to a single Gaussian and show that current amplitudes in both patches represent homogeneous conductance class channels. Mean amplitudes are 3.3 ± 0.1 pA (AChRɛ^−/−) and 5.4 ± 0.2 pA (wt). (C) Current-voltage (I–V) relations of single end plate channels in P30 wild-type (open symbols) and AChRɛ^−/− muscle (solid symbols). Voltage (V) represents shift of patch-membrane potential from extrapolated current reversal potential. Straight lines (not shown) were fitted to data points in the voltage range of −20 mV to −100 mV. Slope conductance is 32 pS (AChRɛ^−/−) and 52 pS (wt), respectively. Different experiment from that shown in A and B.