Increased dendritic membrane excitability persists in fifteen week atrophic SCA1 Purkinje neurons.

(A) Representative dendritic whole-cell patch clamp recordings from a fifteen week old wild-type Purkinje neuron (soma-to-patch distance: 45.0 μm) and fifteen week old ATXN1[82Q] Purkinje neuron (soma-to-patch distance: 48.6 μm). Traces have been aligned at the threshold of the spike. (B) Scatter-plots with single-exponent decay best-fit lines for back-propagating action potential (bAP) amplitude measurements in wild-type and ATXN1[82Q] Purkinje neurons at fifteen weeks of age show less attenuation of bAPs in ATXN1[82Q] mice. Each data point represents a recording from a separate cell. Best-fit line is an exponential decay model with two parameters, of the form y = Aebx, consistent with a previous study of action potential backpropagation in Purkinje neurons [37] and showing R2 values of 0.9834 (wild-type) and 0.9346 (ATXN1[82Q]). (C) Scatter-plots with single-exponent growth best-fit lines for bAP half-width measurements in wild-type and ATXN1[82Q] Purkinje neurons at fifteen weeks of age show wider bAPs in ATXN1[82Q] mice. Each data point represents a recording from a separate cell. Best-fit line is an exponential growth model with two parameters, of the form y = Aebx. (D) Representative action potential from a somatic whole-cell recording in wild-type and ATXN1[82Q] Purkinje neurons at fifteen weeks of age. The peak-to-trough amplitude of action potentials (summarized in (E)) and the action potential half-width (summarized in (F)) recorded at the soma do not differ significantly between wild-type and ATXN1[82Q] Purkinje neurons at fifteen weeks of age. In (B, C, E, and F) N = 5–10 mice were utilized per genotype. Where error bars are present, data are mean ± SEM. * = P<0.05; NS = Not significant. Statistical significance derived by extra sum of squares F test to determine whether one should reject the null hypothesis that data are best described by a single curve rather than two curves separated by genotype (B, C) or unpaired two-tailed Student’s T-Test (E, F).