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Physiol Behav. 2016 Oct 1;164(Pt A):383-9. doi: 10.1016/j.physbeh.2016.06.006. Epub 2016 Jun 11.

Effects of intrinsic aerobic capacity and ovariectomy on voluntary wheel running and nucleus accumbens dopamine receptor gene expression.

Author information

1
Nutrition and Exercise Physiology, University of Missouri, Columbia, MO, USA.
2
Nutrition and Exercise Physiology, University of Missouri, Columbia, MO, USA; Child Health, University of Missouri, Columbia, MO, USA; Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA.
3
Psychological Sciences, University of Missouri, Columbia, MO, USA.
4
Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, MI, USA.
5
Biomedical Sciences, University of Missouri, Columbia, MO, USA.
6
Department of Molecular Integrative Physiology, University of Kansas Medical Center, Kansas City, KS, USA.
7
Nutrition and Exercise Physiology, University of Missouri, Columbia, MO, USA. Electronic address: vieirapotterv@missouri.edu.

Abstract

Rats selectively bred for high (HCR) and low (LCR) aerobic capacity show a stark divergence in wheel running behavior, which may be associated with the dopamine (DA) system in the brain. HCR possess greater motivation for voluntary running along with greater brain DA activity compared to LCR. We recently demonstrated that HCR are not immune to ovariectomy (OVX)-associated reductions in spontaneous cage (i.e. locomotor) activity. Whether HCR and LCR rats differ in their OVX-mediated voluntary wheel running response is unknown.

PURPOSE:

To determine whether HCR are protected from OVX-associated reduction in voluntary wheel running.

METHODS:

Forty female HCR and LCR rats (age ~27weeks) had either SHM or OVX operations, and given access to a running wheel for 11weeks. Weekly wheel running distance was monitored throughout the intervention. Nucleus accumbens (NAc) was assessed for mRNA expression of DA receptors at sacrifice.

RESULTS:

Compared to LCR, HCR ran greater distance and had greater ratio of excitatory/inhibitory DA mRNA expression (both line main effects, P<0.05). Wheel running distance was significantly, positively correlated with the ratio of excitatory/inhibitory DA mRNA expression across animals. In both lines, OVX reduced wheel running (P<0.05). Unexpectedly, although HCR started with significantly greater voluntary wheel running, they had greater OVX-induced reduction in wheel running than LCR such that no differences were found 11weeks after OVX between HCROVX and LCROVX (interaction, P<0.05). This significant reduction in wheel running in HCR was associated with an OVX-mediated reduction in the ratio of excitatory/inhibitory DA mRNA expression.

CONCLUSION:

The DA system in the NAc region may play a significant role in motivation to run in female rats. Compared to LCR, HCR rats run significantly more, which associates with greater ratio of excitatory/inhibitory DA mRNA expression. However, despite greater inherent motivation to run and an associated brain DA mRNA expression profile, HCR rats are not protected against OVX-induced reduction in wheel running or OVX-mediated reduction in the ratio of excitatory/inhibitory DA receptor mRNA expression. OVX-mediated reduction in motivated physical activity may be partially explained by a reduced ratio of excitatory/inhibitory DA receptor mRNA expression for which intrinsic fitness does not confer protection.

KEYWORDS:

Aerobic capacity; Dopamine receptors; Exercise motivation; Nucleus accumbens; Ovariectomy

PMID:
27297873
PMCID:
PMC4983202
DOI:
10.1016/j.physbeh.2016.06.006
[Indexed for MEDLINE]
Free PMC Article

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