Naltrexone induces arcuate nucleus neuropeptide y gene expression
in the rat.
Kotz, C. M., Grace, M. K., Briggs, J., Billington, C. J. and Levine,
A. S.
Departments of Food Science and Nutrition, Psychiatry and Medicine,
University of Minnesota, 1334 Eckles Avenue, Saint Paul, MN 55108,
USA, and Veterans Affairs Medical Center, One Veterans Drive,
Research Route 151, Minneapolis, MN 55417, USA.
APStracts 3:0081R, 1996.
Neuropeptide Y (NPY) has potent effects on several components of
energy metabolism, including increased feeding and decreased brown
fat thermogenesis. Negative energy balance, such as food deprivation,
increases NPY mRNA in hypothalamic arcuate nucleus (ARC). Naltrexone
(NLTX), an opioid receptor antagonist, decreases NPY-induced feeding.
We hypothesized that NLTX would alter ARC NPY mRNA and change NPY
effects on brown fat. Osmotic minipumps pre-filled with either saline
or NLTX (70 [mu]g/hr) were implanted subcutaneously in 32 male
Sprague Dawley rats. Half were food-deprived and half were allowed
food ad lib for 48 h. Food intake was measured at 24 and 48 h. At 48
h, ARC NPY mRNA and brown fat uncoupling protein (UCP) mRNA levels
were determined using cDNA probes. Forty-eight hour food intake was
significantly decreased by 24% following NLTX infusion. Food
deprivation and NLTX treatment significantly and independently
increased ARC NPY mRNA, and decreased UCP mRNA levels in brown fat,
suggesting a complex interaction between hypothalamic NPY and
endogenous opioids in the regulation of energy balance.
Received 3 April 1995; accepted in final form 22 February 1996.
APS Manuscript Number R222-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 20 March 96