Central Neuropharmacology of D-Ala2-Met-Enkephalinamide and its Interactions with Taurine in Rats

Methionine enkephalin, the amino acid sequence 61–65 (Tyr-Gly­Gly-Phe-Met) of β-lipotropin, and the related peptide leucine enke­phalin (Tyr-Gly-Gly-Phe-Leu) are endogenous ligands for the opiate receptor in the brain (12). These peptides administered icv in rats (2) and mice (6) possess short-lasting and naloxone-sensitive anal­gesic properties. D-Ala2-Met-enkephalinamide (DAME, Tyr-D-Ala-Gly­Phe-Met-CONH2) is an enkephalin analogue and is pharmacologically similar to morphine and β-endorphin (β-LPH61–91); DAME is more potent in the induction of analgesia than methionine enkephalin (24) and elicits the same catalepsy in rats (29) as β-endorphin (4,17,19, 22) .