Figure 7. Effects of La³⁺ on GABA responses in nucleated patches from cerebellar granule cells.

A, averaged response in a nucleated outside-out patch isolated from a cerebellar granule neuron of a rat at the age of P7, induced by 2 ms applications of 1 mM GABA together with the exponential fitting to the current decay and the weighted time constant. LaCl₃ (100 μm) coapplied with GABA and pre-perfused (middle), produced prolongation of the current decay as it can be better observed in the right panel where the traces are shown superimposed. Left panel in B, superimposed traces evoked by two successive applications of 2 ms GABA pulses separated by 25, 50, 100, 200, 400, 600 and 800 ms intervals in a nucleated patch isolated from a P7 rat cerebellar granule neuron. Right panel in B, superimposed traces evoked in the same patch by two successive applications of 2 ms GABA (1 mM) + LaCl₃ (100 μm) pulses separated by increasing intervals. LaCl₃ was also pre-perfused. C, summary of the effects of LaCl₃ on GABA responses in nucleated patches excised from cerebellar granule cells in rats at P7-P8. Amp, amplitude; τ_f and τ_s, deactivation time constants; %Fast, percentage contribution of the fast component of biexponential functions fitted to the current decay. Each bar represents the mean ±s.e.m. of 18 patches studied. * Statistical significance with respect to control (P < 0.05 ANOVA followed by t test). D, comparison of the recovery time course of the second response from the desensitization in the two experimental conditions in nucleated patches excised from cerebellar granule cells in rats at P7-P8. The percentage recovery from desensitization at each interval between two brief GABA pulses is calculated and plotted as in Fig. 3. The τ₁, τ₂, A₁ and A₂ values in the respective experimental conditions are indicated. Note the apparent prevention of desensitization with LaCl₃ pre-perfusion. Each data point represents the mean ±s.e.m. of 11 patches studied.