Document Detail


Distinct, time-dependent effects of voluntary exercise on circadian and ultradian rhythms and stress responses of free corticosterone in the rat hippocampus.
MedLine Citation:
PMID:  19477935     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Previous work has shown that allowing rats to voluntarily exercise in a running wheel for 4 wk modifies the hypothalamic-pituitary-adrenal axis and behavioral coping responses to stress. To investigate whether long-term voluntary exercise would also affect the free, biologically active fraction of corticosterone in the brain, we conducted an in vivo microdialysis study in the hippocampus of rats. We monitored both the baseline circadian and ultradian patterns of corticosterone in hippocampus dialysates over the diurnal cycle and the responses to forced swim and novelty stress at different stages of exercise. Exercise for 1 d, 2 d, or 1 wk did not affect baseline circadian and ultradian pulse parameters or stress-induced hippocampal free corticosterone concentrations suggesting that acute or short-term periods of exercise do not affect baseline and stress-induced hormone levels. Baseline hormone parameters in 4 wk exercised rats, however, showed significantly increased pulse amplitudes (+108%) and mean free corticosterone levels (+42%) between 1500 and 2100 h but not between 0900 and 1500 h. Surprisingly, although our previous work showed substantial changes in stress-evoked plasma (total) corticosterone responses in long-term exercised animals, no differences in stress-induced hippocampal free hormone responses could be observed between exercised and sedentary animals. This lack of differences was not caused by compensatory changes in plasma corticosteroid-binding-globulin binding levels in exercising rats. Thus, long-term exercising rats show anticipatory increases in glucocorticoid output before the start of the active phase. These rats also reveal the putative existence of a containment mechanism preventing overexposure of the brain to glucocorticoid hormones.
Authors:
Susanne K Droste; Andrew Collins; Stafford L Lightman; Astrid C E Linthorst; Johannes M H M Reul
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2009-05-28
Journal Detail:
Title:  Endocrinology     Volume:  150     ISSN:  1945-7170     ISO Abbreviation:  Endocrinology     Publication Date:  2009 Sep 
Date Detail:
Created Date:  2009-08-24     Completed Date:  2009-09-16     Revised Date:  2010-09-27    
Medline Journal Info:
Nlm Unique ID:  0375040     Medline TA:  Endocrinology     Country:  United States    
Other Details:
Languages:  eng     Pagination:  4170-9     Citation Subset:  AIM; IM    
Affiliation:
Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, Clinical Science South Bristol, University of Bristol, Bristol BS1 3NY, United Kingdom.
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MeSH Terms
Descriptor/Qualifier:
Animals
Circadian Rhythm / physiology*
Corticosterone / blood*
Hippocampus / metabolism*
Immersion
Male
Microdialysis
Motor Activity / physiology*
Physical Conditioning, Animal / physiology
Rats
Rats, Sprague-Dawley
Stress, Psychological
Swimming
Time Factors
Transcortin / metabolism
Grant Support
ID/Acronym/Agency:
082628//Wellcome Trust; 082628//Wellcome Trust
Chemical
Reg. No./Substance:
0/Serpina6 protein, rat; 50-22-6/Corticosterone; 9010-38-2/Transcortin
Comments/Corrections

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