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This Article Full Text Full Text (PDF) All Versions of this Article: 296/6/R1687    most recent 00019.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Harris, R. B. S. Articles by Bartness, T. J. PubMed PubMed Citation Articles by Harris, R. B. S. Articles by Bartness, T. J.

APPETITE, OBESITY, AND DIGESTION

Testosterone replacement does not normalize carcass composition in chronically decerebrate male rats

¹Department of Biology, Georgia State University, Atlanta, Georgia; ²Department of Foods and Nutrition, University of Georgia, Athens, Georgia; ³Department of Psychology, University of Pennsylvania, Philadelphia, Pennsylvania; and ⁴Department of Biology & Center for Behavioral Neuroscience, Georgia State University, Atlanta, Georgia

Submitted 13 January 2009 ; accepted in final form 13 April 2009

Chronically decerebrate (CD) rats, in which the forebrain and its descending projections are completely neurally isolated from hindbrain and rostral projections, gain substantial amounts of body fat, lose lean tissue, and have low circulating testosterone concentrations. We tested whether testosterone replacement would normalize body composition of male CD rats. Five groups of rats were used: CD placebo, CD testosterone, control placebo, castrate placebo, and castrate testosterone. Testosterone replacement was initiated at the first stage of CD surgery in both CDs and castrate controls. The second stage of CD surgery occurred 8 days later, and the study ended 15 days later. Testosterone implants produced 10-fold normal circulating concentrations. Food intake was fixed for all rats by tube feeding. CD rats had substantially more body fat and less lean tissue than neurally intact rats. Testosterone replacement did not affect adiposity of CD rats but did increase carcass water content. Energy expenditure of CD rats was significantly lower than that of control placebo and castrated rats. Testosterone lowered respiratory equivalency ratio and ameliorated a fall in energy expenditure late in the intermeal interval in CD rats. Castration increased, and testosterone decreased luteinizing hormone (LH) and follicle stimulating hormone (FSH) in neurally intact controls. LH was undetectable, and FSH was equivalent to neurally intact controls in CD rats, and neither was affected by testosterone. Collectively, low testosterone did not explain obesity or decreased lean body mass of CD rats, although CD rats exhibited abnormal levels of circulating reproductive hormones and disrupted testosterone negative feedback.

caudal brainstem; white adipose tissue; energy expenditure; body composition