Early Post‐Natal Maternal Effects on Voluntary Exercise, Maximal Aerobic Capacity, and Associated Traits in Mice

Abstract

During the suckling period, many mammals progress through numerous developmental milestones, including critical periods of the central nervous system, musculoskeletal system, and cardiovascular system – each an important element of physical activity and exercise capacity. In a novel experimental mouse model, four replicate lines were selectively bred for ~90 generations for high voluntary wheel‐running behavior (high‐runner; HR) while four non‐selected Control (C) lines were also maintained. As a result of selection, HR mice run approximately 3‐fold the distances of C mice on a daily basis. Various other physiological and behavioral differences have also evolved in the HR lines, including higher maximal oxygen consumption (VO2max). The aim of the present study was to assess the role of the maternal environment during the birth‐weaning period in the expression of the many differences between HR and C lines using a cross‐fostering paradigm. Cross‐fostering HR mice to C dams (and vice versa) at birth and until weaning allowed us to determine the relative contribution of genetic and early environmental factors in shaping the HR phenotype. Mice were weaned three weeks after birth, housed in same‐sex cages of four, and adult testing began at approximately six weeks of age with measurement of VO2max, daily wheel running over a six‐day period, food consumption, home‐cage activity, body fat composition, and organ masses following dissection. As expected, HR mice ran approximately ~3‐fold more revolutions/day on wheels than their C counterparts. Preliminary analyses show that rearing by an HR dam has a negative effect on adult wheel running in females. This result suggests that the maternal environment provided by HR dams during the suckling period may play a role in the selection limit observed in HR lines.Support or Funding InformationNSF GRFP