Changes in Hypothalamic Met-Enkephalin Levels of Rats Induced by Painful Stimulation and Morphine Treatment

Abstract

The possible influence of painful stimulation and morphine analgesia on hypothalamic met-enkephalin levels, and the possible correlation between this bio-chemical parameter and animal behaviour was studied. The results indicate that both painful stimulation and morphine treatment induce an increase in hypothalamic met-enkephalin. On the other hand, naloxone did not cause any Variation. In animals sub-mitted to painful stimulus, morphine treatment induced a decrease in hypothalamic met-enkephalin levels. Finally, when both morphine and naloxone were administrated before nociceptive stimulation, much higher levels were measured. There was no correlation between the level of hypothalamic met-enkephalin and the pain rating.