AJP - Regulatory, Integrative and Comparative Physiology, Vol 241, Issue 3 173-R184, Copyright © 1981 by American Physiological Society
Pituitary beta-endorphin, naloxone, and feeding in several experimental obesities
M. W. Gunion and R. H. Peters
The role of beta-endorphin in the development of several obesity syndromes
was examined. Adult female hooded rats received ventromedial hypothalamic
lesions, dorsolateral tegmental lesions, parasagittal hypothalamic knife
cuts, intraventricular 5,7-dihydroxytryptamine, ovariectomy, control
surgery, or were deprived to 75% of normal body weight. Dose-dependent
suppression of food intake by the opiate antagonist naloxone (0.5, 1.8,
6.8, or 25.0 mg/kg, ip) was measured during once-daily 4-h food access
periods. No difference was found among the groups at any dose. Pituitary
beta-endorphinlike immunoreactivity (BELI) was substantially decreased in
knife-cut rats, but was unaltered by other treatments. Obesity had no
effect on BELI. In another experiment, rats made obese by prolonged
maintenance on palatable foods had elevated pituitary BELI levels. Feeding
mechanisms involving opioid peptides do not appear to be of etiological
significance in the syndromes examined.
