Locus coeruleus galanin expression is enhanced after exercise in rats selectively bred for high capacity for aerobic activity

The neuropeptide galanin extensively coexists with norepinephrine in locus coeruleus (LC) neurons. Previous research in this laboratory has demonstrated that unlimited access to activity wheels in the home cage increases mRNA for galanin (GAL) in the LC, and that GAL mediates some of the beneficial effects of exercise on brain function. To assess whether capacity for aerobic exercise modulates this upregulation in galanin mRNA, three heterogeneous rat models were tested: rats selectively bred for (1) high intrinsic (untrained) aerobic capacity (High Capacity Runners, HCR) and (2) low intrinsic aerobic capacity (Low Capacity Runners, LCR) and (3) unselected Sprague–Dawley (SD) rats with and without free access to running wheels for 3 weeks. Following this exercise protocol, mRNA for tyrosine hydroxylase (TH) and GAL was measured in the LC. The wheel running distances between the three models were significantly different, and age contributed as a significant covariate. Both selection and wheel access condition significantly affected GAL mRNA expression, but not TH mRNA expression. GAL was elevated in exercising HCR and SD rats compared to sedentary rats while LCR rats did not differ between conditions. Overall running distance significantly correlated with GAL mRNA expression, but not with TH mRNA expression. No strain differences in GAL or TH gene expression were observed in sedentary rats. Thus, intrinsic aerobic running capacity influences GAL gene expression in the LC only insofar as actual running behavior is concerned; aerobic capacity does not influence GAL expression in addition to changes associated with running.

Research highlights▶ Selection for running capacity dramatically influences running behavior. ▶ Greater overall running distance is related to more robust galanin mRNA upregulation in the locus coeruleus.