AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 4 946-R950, Copyright © 1990 by American Physiological Society
Central nervous system injection of dynorphin-(1-13) overrides gastric satiety factors in sheep
M. A. Della-Fera, C. A. Baile, B. D. Coleman, J. L. Miner and J. A. Paterson
Department of Internal Medicine, Washington University School of Medicine, St. Louis 63110.
Signals from the gastrointestinal (GI) tract, arising during ingestion and
digestion of food, are important in the termination of feeding. This study
was carried out to determine whether the satiety triggered by specific GI
stimuli in sheep could be reversed by central nervous system (CNS)
administration of dynorphin, a putative endogenous kappa-opiate receptor
ligand, which has been shown to be a potent feed-intake stimulant in many
species. Rumen distension and increased intraruminal concentration of
propionic acid (an energy substrate produced during fermentation in the
rumen) both significantly decreased feed intake in fasted sheep. When
either of these stimuli were combined with continuous 60-min lateral
cerebroventricular injection of [D-Ala2]dynorphin A-(1-13) (0.32 nmol/min),
feed intake returned to control levels. Increasing feed intake in
food-producing animals is an important way of improving production
efficiency. The findings of these experiments illustrate how manipulation
of a CNS opioid system can modify the effects of feed intake-limiting
factors generated by ingestion of a meal, thereby promoting greater feed
intake.
