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. 2015 Apr 29;35(17):6752–6769. doi: 10.1523/JNEUROSCI.2663-14.2015

Figure 6.

Figure 6.

Membrane hyperpolarization rescues repetitive firing in Purkinje neurons transduced with Fgf14-targeted shRNA. A–D, Representative evoked firing recorded in nontargeted (A,C) and Fgf14-targeted (B,D) shRNA-transduced Purkinje neurons in response to membrane depolarization from a hyperpolarized membrane potential. Removal of a (500 pA) hyperpolarizing current injection resulted in spontaneous firing in most (20 of 25) of the nontargeted shRNA-transduced Purkinje neurons (A) and in 19 of 41 Fgf14-targeted shRNA-transduced Purkinje neurons: 10 of these cells fired tonically and 9 adapted; the remaining (12) cells were silent. Depolarizing (1000 pA) current injections (250 ms) after membrane hyperpolarization elicited high-frequency repetitive firing in most (23 of 25) Purkinje neurons expressing the nontargeted shRNA, as well as in most (39 of 41) Purkinje neurons expressing the Fgf14-targeted shRNA (D). Mean ± SEM firing frequencies in nontargeted and Fgf14-targeted shRNA-transduced Purkinje neurons in response to (250 ms) depolarizing current injections of varying amplitudes presented after membrane hyperpolarization are plotted in E. Firing rates were indistinguishable (two-way ANOVA) in nontargeted and Fgf14-targeted shRNA-transduced Purkinje neurons. F, Inverse cumulative frequency plots of numbers of action potentials evoked by 250 ms, 1000 pA depolarizing current injections after membrane hyperpolarization (Vhyp) in nontargeted and Fgf14-targeted shRNA-transduced Purkinje neurons are plotted. Histograms of spike numbers elicited from rest (Vrest) are replotted from Figure 3H for comparison purposes. Membrane hyperpolarization significantly (p < 0.0001) shifted the frequency distributions to the right (more spikes) in both nontargeted shRNA and Fgf14-targeted shRNA-transduced Purkinje neurons. In addition, the distribution of spikes evoked from a hyperpolarized potential in Fgf14-targeted shRNA-transduced Purkinje neurons is not significantly different from the distribution of spikes evoked from rest in Purkinje neurons expressing the nontargeted shRNA.