Figure 5.

Moderation of input resistance by tonic activation of GABA_ARs is weaker in Ts65Dn GCs. (A) Superimposed traces of voltage-recordings during constant current injections (from −10 pA to action potential threshold in +2 pA increments) from a wild-type GC before (filled circle) and after inhibition of tonically-activate GABA_ARs with 10 μM SR95531 (empty circle). Current values normalised by input capacitance are also indicated. (B) Same as (A), but for a Ts65Dn GC (filled and empty triangles). (C) Subthreshold voltage–current relationships (mean ± SEM) for mature wild-type and Ts65Dn GCs before (control) and after application of SR95531 (WT, n = 24 – 14; Ts65Dn, n = 13 – 8). Dotted lines denote resting membrane potential. Solid lines are fitted sigmoidal curves. In control, the relationships diverged for current injections greater than +2 pA (*f₁,₂₇ = 5.6, p = 0.025, two-way repeated measures ANOVA). In SR95531, the relationships were indistinguishable (the same sigmoidal curve is fitted to both sets of data points as an F-test did not reveal differences in the parameters of curves fitted to each data set, F(4,8) = 1.094, p = 0.4214). (D) Plots of input resistance against membrane potential in control and in the presence of SR95531, obtained by differentiating fitted lines in (C).