β-endorphin-induced hyperthermia in the cat

β -Endorphin was injected into the third cerebral ventricle (ICV) of conscious, unrestrained cats. Hyperthermic responses to 50 μ g of this peptide were reduced by 20–100 μ g naloxone given ICV 1 hr later. A dose of 40 μ g β -endorphin increased body temperature at ambient temperatures of 4, 22 and 34°C, with the response being greater the warmer the environment. These results indicate that β -endorphin acts on a central naloxone-sensitive, receptor which is probably the ν 2 receptor that is activated by low doses of D-Ala 2 -Met-enkephalinamide to evoke a similar pattern of change in body temperature over a comparable range of ambient temperatures.