Skeletal muscle contractile dysfunction in the HD mouse models.

<p>(A) Twitch stimuli were delivered to elicit TTP (time to peak) contraction of the hind limb EDL and TA skeletal muscles. A significant increase in TTP in the R6/2 skeletal muscles was observed for EDL but not TA at 12 and 14 weeks of age. (B) Twitch stimuli were delivered to elicit a half-relaxation time of the hind limb EDL and TA muscles. A significant increase in the half-relaxation time in R6/2 skeletal muscles was observed for both EDL and TA at 12 and 14 weeks of age. Error bars are SEM (n = 10). ONE-WAY ANOVA with Bonferroni <i>post-hoc</i> test: *<i>p</i> < 0.05, **<i>p</i> < 0.01; ***<i>p</i> < 0.001. Transcriptional deregulation of contractile transcripts: (C) <i>Tnn1</i> (Troponin 1, slow), (D) <i>Tnn3</i> (Troponin3, fast), (E) <i>Myh7</i> (myosin heavy light chain 7), (F) <i>Myh2</i> (myosin heavy light chain 2) mRNAs were significantly deregulated in the muscle of R6/2 and <i>Hdh</i>Q150 mice. All Taqman qPCR values were normalized to the geometric mean of three housekeeping genes: <i>Atp5b</i>, <i>Yhwaz</i> and <i>Rpl13a</i>. Error bars are SEM (n = 6). Student’s <i>t</i>-test: *<i>p</i> < 0.05, **<i>p</i> < 0.01; ***<i>p</i> < 0.001.