AJP - Regulatory, Integrative and Comparative Physiology, Vol 270, Issue 1 111-R117, Copyright © 1996 by American Physiological Society
Dissociation of hypothalamic NPY from BAT uncoupling protein mRNA in rats exposed to 24 h thermoneutrality
C. Bing, H. Frankish, Q. Wang, D. Hopkins, J. Keith, P. Trayhurn and G. Williams
Department of Medicine, University of Liverpool, United Kingdom.
Neuropeptide Y (NPY) is increasingly considered to be involved in the
central regulation of energy balance. Our previous studies suggest that
hypothalamic NPY neurons of the arcuatoparaventricular (ARC-PVN) projection
are inhibited in association with the marked increases in brown adipose
tissue (BAT) thermogenesis and uncoupling protein (UCP) gene expression in
rats exposed to cold. We therefore hypothesized that the NPYergic ARC-PVN
system would be activated in a thermoneutral environment, when energy
expenditure falls to a minimum, and that this activation could mediate the
fall in BAT activity. We measured regional hypothalamic NPY concentrations,
hypothalamic NPY receptor binding, and NPY mRNA together with UCP mRNA
levels in rats exposed to thermoneutrality (29 degrees C) for 24 h. At
thermoneutrality, UCP mRNA levels fell to 42% of those in controls
maintained at 22 degrees C, but there were no significant changes in
hypothalamic NPY or NPY mRNA levels or in NPY receptor binding. We conclude
that the fall in UCP mRNA expression occurring under short-term
thermoneutral condition is mediated by neuroendocrine mechanisms other than
increased activity of hypothalamic NPY neurons.
