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Melatonin influences the release of endogenous opioid peptides in rat periaqueductal gray

Yu Changxi, Wu Gencheng, Xu Shaofen, Chen Chonghong

State Key Laboratory of Medical Neurobiology,Department of Neurobiology,Shanghai Medical University.Shanghai 200032；China

Abstract

The present study was undertaken to explore central mechanisms underlying the analgesic effect of melatonin. Push-pull perfusion technique and radioimmunoassay were used to observe the changes in the contents of #beta#-endorphin (#beta#-Fp) and leucine0enkephalin (L-EK) in the perfusate from the rat periaqueductal gray (PAG) after administration of melatonin. 30-50 min after an intraperitoneal injection of melatonin (110mg/kg), the #beta#-Ep content in the perfusate was increased significantly, while the L-EK content was not changed. Pain threshold was measured using the warm water tail-flick test during the push-pull perfusion of the PAG. It was found that the rat pain threshold was increased significantly 40 min after the intraperitoneal injection of melatonin (110mg/kg).

Key words: Melatonin;#beta#-endorphin;Enkephalin;Periaqueductal gray;Analgesia;Rat

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Citing This Article：

Yu Changxi, Wu Gencheng, Xu Shaofen, Chen Chonghong. Melatonin influences the release of endogenous opioid peptides in rat periaqueductal gray. Acta Physiol Sin 2000; 52 (3): (in Chinese with English abstract).