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1 Biology, Georgia State University, Atlanta, Georgia, United States
2 Foods and Nutrition, University of Georgia, Athens, Georgia, United States
3 Centre de Recherche de l'Hopital Laval, Sainte-Foy , Canada
4 Dept. of Biology, Georgia State University, Atlanta,, Georgia, United States
* To whom correspondence should be addressed. E-mail: bartness{at}gsu.edu.
A precise understanding of neural circuits controlling lipid mobilization and thermogenesis remains to be determined. We have been studying the sympathetic nervous system (SNS) contributions to white adipose tissue (WAT) lipolysis largely in Siberian hamsters. Central melanocortins are implicated in the control of the sympathetic outflow to WAT and, moreover, the melanocortin 4 receptors (MC4-R) appear to be principally involved. We previously found that acute 3rd ventricular melanotan II (MTII; a MC3/4-R agonist) injections increase sympathetic drive (norepinephrine turnover) to interscapular brown adipose tissue (IBAT) and IBAT temperature. Here we tested whether MC4-R mRNA is expressed in IBAT SNS outflow neurons using in situ hybridization for the former and injections of the transneuronal viral retrograde tract tracer, pseudorabies virus (PRV) into IBAT, for the latter. Significant numbers of double-labeled cells for PRV and MC4-R mRNA were found across the neuroaxis (mean of all brain sites ~60%) including the hypothalamic paraventricular nucleus (PVH; ~80%). Acute parenchymal MTII microinjections into the PVH of awake, freely-moving hamsters, using doses below those able to increase IBAT temperature when injected into the 3rd ventricle, increased IBAT temperature for as long as 4 h, as measured by temperature transponders implanted below the tissue. Collectively, these data add significant support to the view that central melanocortins are important in controlling IBAT thermogenesis via the SNS innervation of this tissue likely through the MC4-Rs.
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C. K. Song, G. J. Schwartz, and T. J. Bartness Anterograde transneuronal viral tract tracing reveals central sensory circuits from white adipose tissue Am J Physiol Regulatory Integrative Comp Physiol, March 1, 2009; 296(3): R501 - R511. [Abstract] [Full Text] [PDF] |
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