title: Beta-endorphin: effect on thermoregulation in aged monkeys.
abstract: In previous experiments small doses of the opiate morphine produced greater hyperthermia in aged than in younger sub-human primates. To test whether this augmented response is due to enhanced sensitivity of CNS opioid receptors with age, beta-endorphin (0.625-5 micrograms), an endogenous opioid peptide, was injected into the lateral cerebral ventricle (ICV) of young (less than 9 years) and aged (greater than 9 years) squirrel monkeys. Significantly greater hyperthermias developed in the older primates after each dose. In the aged monkeys, all but the smallest dose increased core temperature about 1.5 degrees C within 1 hr after injection. Mean rectal temperature in the younger animals rose 0.5-0.7 degrees after all but the largest dose (1-1.5 degrees C rise). Both groups maintained an elevated body temperature after central beta-endorphin throughout the 5 hr recording period. 1.25 micrograms beta-endorphin given ICV in a hot environment (30 degrees C) caused greater hyperthermia in older animals. This dose given in the cold (18 degrees C) caused large changes in temperature of the aged monkeys, either hyperthermia or marked decreases, whereas the young primates developed only moderate rises in body temperature. The same dose of morphine sulfate (1.25 micrograms) ICV produced similar changes in core temperature in the two age groups in each ambient temperature. These results indicate that: (1) stimulation of CNS opioid receptors influences thermoregulation and (2) aging increases responsiveness to such stimulation.
mesh_terms: D000367:Age Factors; D000818:Animals; D001833:Body Temperature Regulation / Q000187:drug effects*; D001921:Brain / Q000187:drug effects* / Q000502:physiology; D004723:Endorphins / Q000494:pharmacology* / Q000502:physiology; D005260:Female; D007276:Injections, Intraventricular; D008297:Male; D009020:Morphine / Q000494:pharmacology; D012453:Saimiri; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D001615:beta-Endorphin; D009020:Morphine