The purpose of the current study was to partially phenotype male and female rats from generations 8-10 (G8-G10) that had been selectively-bred to possess low (LVR) vs. high (HVR) voluntarily running behavior. Over the first 6 days with wheels, 34 day-old G8 male and female LVRs ran shorter distances (p < 0.001), spent less time running (p < 0.001) and ran slower (p < 0.001) than their G8 male and female HVR counterparts, respectively. HVR and LVR lines consumed similar amounts of standard chow with or without wheels. No inherent difference existed in PGC1α mRNA in the plantaris and soleus muscles of LVR and HVR non-runners, although G8 LVR rats inherently possessed less NADH-positive superficial plantaris fibers compared to G8 HVR rats. While day-28 body mass tended to be greater in both sexes of G9-10 LVR non-runners versus G9-10 HVR non-runners (p = 0.06), body fat percentage was similar between lines. G9-10 HVRs had fat mass loss after 6 days of running compared to their pre-running values, while LVR did not lose or gain fat mass during the 6-day voluntary running period. RNA deep sequencing efforts in the nucleus accumbens showed only 8 transcripts to be > 1.5-fold differentially expressed between lines in HVR and LVR non-runners. Interestingly, HVRs presented less Oprd1 mRNA which ties in to potential differences in dopaminergic signaling between lines. Future studies using this model will continue to examine if exercise motivation is different between these lines and, if so, how it is mechanistically regulated.
- selective breeding
- nucleus accumbens
- Copyright © 2012, American Journal of Physiology - Regulatory, Integrative and Comparative Physiology