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

Pharmacol Biochem Behav. 1979 Oct;11(4):407-11. doi: 10.1016/0091-3057(79)90116-3.


Rats were given four daily, interperitoneal injections (80 micrograms/kg) of Met-enkephalin, (D-Ala2)-Met-enkephalin-NH2, beta-endorphin, (D-Ala2)-beta-endorphin or the diluent (0.9% NaCl acidified to, 0.01 M with acetic acid). Animals were subsequently tested for food and water inake 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. beta-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.

MeSH terms

  • Animals
  • Drinking Behavior / drug effects*
  • Emotions / drug effects
  • Endorphins / administration & dosage
  • Endorphins / pharmacology*
  • Enkephalins / administration & dosage
  • Enkephalins / pharmacology*
  • Feeding Behavior / drug effects*
  • Injections, Intraperitoneal
  • Male
  • Motor Activity / drug effects*
  • Rats


  • Endorphins
  • Enkephalins