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Endocannabinoids, anandamide, exercise, physical activity, neurogenesis, stereotypy, MR volumetry, MR spectroscopy, hippocampus, C57BL/6 mice
Abstract:
Beneficial effects of voluntary wheel running on hippocampal
neurogenesis, morphology and hippocampal-dependent behavior have widely
been studied in rodents, but also serious side effects and similarities
to stereotypy have been reported. Some mouse strains run excessively
when equipped with running wheels, complicating the comparability to
human exercise regimes. Here, we investigated how exercise restriction
to 6 h/day affects hippocampal morphology and metabolism, stereotypic
and basal behaviors, as well as the endocannabinoid system in wheel
running C57BL/6 mice; the strain most commonly used for behavioral
analyses and psychiatric disease models. Restricted and unrestricted
wheel running had similar effects on immature hippocampal neuron
numbers, thermoregulatory nest building and basal home-cage behaviors.
Surprisingly, hippocampal gray matter volume, assessed with magnetic
resonance (MR) imaging at 9.4 Testa, was only increased in unrestricted
but not in restricted runners. Moreover, unrestricted runners showed
less stereotypic behavior than restricted runners did. However, after
blockage of running wheels for 24 h stereotypic behavior also increased
in unrestricted runners, arguing against a long-term effect of wheel
running on stereotypic behavior. Stereotypic behaviors correlated with
frontal glutamate and glucose levels assessed by H-1-MR spectroscopy.
While acute running increased plasma levels of the endocannabinoid
anandamide in former studies in mice and humans, we found an inverse
correlation of anandamide with the daily running distance after
long-term running. In conclusion, although there are some diverging
effects of restricted and unrestricted running on brain and behavior,
restricted running does not per se seem to be a better animal model for
aerobic exercise in mice. (C) 2016 Elsevier Inc. All rights reserved.
