Melatonin Analgesic Effect And Its Mechanism

THE STUDY ON THE ANALGESIC EFFECT OF MELATONIN IN THE NERVE CENTRE AND ITS MECHANISM ZOU DAN (PHARMACOLOGY) LI JINGCAI PROFESSOR ABSTRACT Taking the unit discharge of the neurons in posterior group of the thalamic nuclei (P0) evoked by stimulating greater splanchnic nerve (GSN) as an index of visceral pain , the effects of melatonin(MT) ,the living substance secreted mainly by pineal gland ,on this kind of pain discharge were studied by using extracellular microelectrode record and stereotaxie techniques .The research method well showed the analgesic effect of MT in the nerve center and it could provide new experiment data to reveal one aspect of MT analgesic mechanism It turned out that IvlT manifested a dose? dependent inhibition to one or two clusters evoked 3 unit discharge of P0 and possessed a significant circadian rhythm .The result also showed that MT had analgesic activity to fast pain and slow pain which conducted by A 5 and C nerve fibers respectively . Naloxone, the opiate antagonist, could partially block the analgesic effect of MT . It indicated that opiate system was involved in MT analgesia process .Moreover ,the analgesic action of MT to the first component of the unit discharges conducted by A ~ nerve fibers was blocked by the muscarinic cholinergic antagonist Atropine injected into lateral ventricles. To the second component conducted by C nerve fibers , Atropine could not affect the analgesic action of MT .The experiment result also noted that atropine could reinforce inhibition function of Morphine to the first and second components , thus MT might has a different anagesic mechanism from that of morphine It is suggested that MT has analgesic effect to visceral pain at thalamus level and the cholinergic system as well as the opiate system 4 may be involved in this process...