Mechanisms of altered skeletal muscle action potentials in the R6/2 mouse model of Huntington's disease.

Mechanisms of altered skeletal muscle action potentials in the R6/2 mouse model of Huntington's disease. Am J Physiol Cell Physiol. 2020 May 20;: Authors: Miranda DR, Reed E, Jama A, Bottomley M, Ren H, Rich MM, Voss AA Abstract Huntington's disease (HD) patients suffer from progressive and debilitating motor dysfunction for which only palliative treatment is currently available. Previously, we discovered reduced skeletal muscle Cl- channel (ClC-1) and inwardly rectifying K+ channel (Kir) currents in R6/2 HD transgenic mice. To further investigate the role of ClC-1 and Kir currents in HD skeletal muscle pathology, we measured the effect of reduced ClC-1 and Kir currents on action potential (AP) repetitive firing in R6/2 mice using two-electrode current-clamp. We found that R6/2 APs had a significantly lower peak amplitude, depolarized maximum repolarization, and prolonged decay time compared to WT. Of these differences, only the maximum repolarization was accounted for by the reduction in ClC-1 and Kir currents, indicating the presence of additional ion channel defects. We found that both KV1.5 and KV3.4 mRNA levels were significantly reduced in R6/2 skeletal muscle compared to WT, which explains the prolonged decay time of R6/2 APs. Overall, we found that APs in WT and R6/2 muscle significantly and progressively change during activity to maintain peak amplitude, despite build-up of Na+ channel inactivation. Even with this resilience...
Source: Am J Physiol Cell Ph... - Category: Cytology Authors: Tags: Am J Physiol Cell Physiol Source Type: research