Fig. 3. Variable membrane conductance and ion channel expression in single lateral pyloric (LP) neurons of the crab stomatogastric ganglion. (A) Two LP neurons from two different animals show robust conservation of output. (B) Two-electrode voltage clamp measures of three K⁺ conductances (I_Kd=delayed rectifier, I_K[Ca]=calcium-activated K⁺, I_A=fast-transient A-type) in LP neurons from nine different animals reveals that neurons with functionally similar outputs show highly variable levels of membrane conductances. (C) Quantitative PCR measures of expression of three K⁺ channels that carry the conductances measured in Fig. 3B (shab [I_Kd], BK-KCa [I_K[Ca]], shal [I_A]) in the same LP neurons. The same level of variability exists at the level of gene expression and membrane conductance. These data combined with correlations between measured membrane conductance and ion channel expression in LP neurons of the crab (D) demonstrate that this variability is biologically meaningful and not the result of `noise' in either the voltage clamp recordings or the quantitative analyses of gene expression. These data suggest that these neurons continually adjust their intrinsic properties via activity-dependent processes in order to maintain consistent functional output. Figure adapted from Schulz et al. (Schulz et al., 2006) and reproduced with permission. LP recordings courtesy of J.-M. Goaillard.