Influence of glycyl-proline (a dipeptide sequence of β-LPH at 43-44 position) on central actions of morphine

Abstract

An endogenous dipeptide, located in 43-44 position of β - LPH chain, markedly antagonises morphine analgesia in rats but has no effect on morphine catatonia. A dose of 50 ug/100 g body weight of it shows about 80% antagonism. The site of its antagonistic action appears to be on the ventral surface of the brain stem. This dipeptide has further been shown to markedly facilitate the development of tolerance to morphine analgesia. Structure-activity relationship of this dipeptide demonstrates that the cationic amino group of glycine and hydrophobic moiety of proline are essential for exhibiting antagonism against morphine analgesia. © 1982.