Abstract
In order to further understand the genetic basis for variation in inherent (untrained) exercise capacity, we examined the brains of 32 male rats selectively bred for high or low running capacity (HCR and LCR, respectively). The aim was to characterize the activation patterns of brain regions potentially involved in differences in inherent running capacity between HCR and LCR. Using quantitative in situ hybridization techniques, we measured messenger ribonuclease (mRNA) levels of c-Fos, a marker of neuronal activation, in the brains of HCR and LCR rats after a single bout of acute treadmill running (7.5–15 minutes, 15° slope, 10 m/min) or after treadmill running to exhaustion (15–51 minutes, 15° slope, initial velocity 10 m/min). During verification of trait differences, HCR rats ran six times farther and three times longer prior to exhaustion than LCR rats. Running to exhaustion significantly increased c-Fos mRNA activation of several brain areas in HCR, but LCR failed to show significant elevations of c-Fos mRNA at exhaustion in the majority of areas examined compared to acutely run controls. Results from these studies suggest that there are differences in central c-Fos mRNA expression, and potential brain activation patterns, between HCR and LCR rats during treadmill running to exhaustion and these differences could be involved in the variation in inherent running capacity between lines.
Highlights
In the last few decades, exercise physiologists have turned to animal models to supplement the ongoing research on the genetic basis for differences in inherent exercise capacity in humans
In terms of distance run, high capacity runners (HCR) ran a maximum distance of 1998628 meters, whereas low capacity runners (LCR) ran a maximum distance of 21266 meters (943% difference; [F (1,30) = 4026; p,0.0001] In addition, HCR ran for a maximum duration of 7260.60 minutes while LCR ran for a maximum duration of 1560.35 minutes [F (1,30) = 6743; p,0.0001])
HCR ran a maximum distance of 1149666 meters, whereas LCR ran a maximum distance of 205626 meters (562% difference; [F (3,28) = 197; p,0.0001])
Summary
In the last few decades, exercise physiologists have turned to animal models to supplement the ongoing research on the genetic basis for differences in inherent (untrained) exercise capacity in humans. In 1996, a large-scale selective breeding program in rats was initiated to create divergent lines of inherent running capacity to serve as substrate to help understand the genetic basis for the variation in maximal running capacity [9,19]. For development of these models, running capacity was assessed at each generation by using an incremental velocity treadmill running protocol to exhaustion when the animals were 11 weeks of age [20]. After 6 generations of selection, the low capacity runners (LCR) and high capacity runners (HCR) differed in inherent running capacity by
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