Figure 1
Tonic GABA A R-mediated current-density is reduced in Ts65Dn cerebellar GCs. (A) Current recordings from a wild-type GC (WT, filled circle) and a Ts65Dn GC (filled triangle) held at −70 mV, before and during application of SR95531 (10 μM, horizontal bar), with a pipette containing a high Cl− concentration (ECl ~0 mV). Current amplitudes have been normalised by input capacitance. Dashed lines indicate mean current remaining after block of GABAARs with SR95531. Asterisks indicate phasic currents. (B) Cumulative distribution of tonic GABAAR-mediated current-densities in mature wild-type (n = 54) and Ts65Dn (n = 38) GCs at a holding potential of −70 mV. Dashed lines point to median values (*p = 0.0192, Mann–Whitney U test). (C) Plots of the variance of the SR-sensitive tonic current against the mean of the SR-sensitive tonic current at a holding potential of −70 mV in wild-type (circles) and Ts65Dn (triangles) GCs. Each point represents a different cell. The line on each plot is drawn through the origin with the same slope of −1.39 pA, which corresponds to the single-channel current, since linear-regression lines fitted to both sets of data did not differ (slope, p = 0.1475; intercept, p = 0.5354, ANCOVA). (D) Plots of current-density (mean ± SEM) against membrane potential, expressed relative to values at −70 mV in wild-type (n = 5, circles) and Ts65Dn (n = 5, triangles) cells. Solid lines are fitted sigmoidal curves.