SYSTEMIC ADMINISTRATION OF MET-ENKEPHALIN, (D-ALA2)-MET-ENKEPHALIN, BETA-ENDORPHIN, AND (D-ALA2)-BETA-ENDORPHIN - EFFECTS ON EATING, DRINKING AND ACTIVITY MEASURES IN RATS

Rats were given four daily, interperitoneal injections (80 μg/kg) of Met-enkephalin, (D-Ala2)-Met-enkephalin-NH2, β-endorphin, (D-Ala2)-β-endorphin or the diluent (0.9% NaCl acidified to, 0.01 M with acetic acid). Animals were subsequently tested for food and water intake and activity. Met-enkephalin injections did not affect any of the measures but its (D-Ala2) analog reduced food intake and some of the activity measures in a complicated way. β-Endorphin injections did not affect food or water intake; in familiar situations these animals were less active while novel situations seemed to potentiate activity. The (D-Ala2) analog reduced wheel running over 24 hours. © 1979.