Regional and genotypic differences in intrinsic electrophysiological properties of cerebellar Purkinje neurons from wild-type and dystrophin-deficient mdx mice

Cerebellar subregions are recognized as having specialized roles, with lateral cerebellum considered crucial for cognitive processing, whereas vermal cerebellum is more strongly associated with motor control. In human Duchenne muscular dystrophy, loss of the cytoskeletal protein dystrophin is thought to cause impairments in cognition, including learning and memory. Previous studies demonstrate that loss of dystrophin causes dysfunctional signaling at gamma-aminobutyric acid (GABA) synapses on Purkinje neurons, presumably by destabilization of GABA(A) receptors. However, potential differences in the intrinsic electrophysiological properties of Purkinje neurons, including membrane potential and action potential firing rates, have not been investigated. Here, using a 2 x 2 analysis of variance (ANOVA) experimental design, we employed patch clamp analysis to compare membrane properties and action potentials generated by acutely dissociated Purkinje neurons from vermal and lateral cerebellum in wild-type (WT) mice and mdx dystrophin-deficient mice. Compared to Purkinje neurons from WT mice, neurons from mdx mice exhibited more irregular action potential firing and a hyperpolarization of the membrane potential. Firing frequency was also lower in Purkinje neurons from the lateral cerebellum of mdx mice relative to those from WT mice. Several action potential waveform parameters differed between vermal and lateral Purkinje neurons, irrespective of dystrophin status, including action potential amplitude, slope (both larger in the vermal region), and duration (shorter in the vermal region). Moreover, the membrane potential of Purkinje neurons from the vermal region of WT mice exhibited a significant hyperpolarization and concurrent reduction in the frequency of spontaneous action potentials compared to Purkinje neurons from the lateral region. This regional hyperpolarization and reduction in spontaneous action potential frequency was abolished in mdx mice. These results from mice demonstrate the presence of differential electrophysiological properties between Purkinje neurons from different regions of the WT mouse cerebellum and altered intrinsic membrane properties in the absence of dystrophin. These findings provide a possible mechanism for the observations that absence of cerebellar dystrophin contributes to deficits in mental function observed in humans and mouse models of muscular dystrophy. Moreover, these results highlight the importance of distinguishing functional zones of the cerebellum in future work characterizing Purkinje neuron electrophysiology and studies using the model of dissociated Purkinje neurons from mice. (C) 2013 Elsevier Inc. All rights reserved.