PharmacologicalResearch Communications, VoL 20, Supplement/, ?988 GLYCINE ANTINOCICEPTIVE EFFECTS IN MICE 57 M.Carrara, S.Zampiron, F.Capolongo, L.Cima and P.Giusti* Department of Pharmacology, University of Padua, 35131 Padova, *Institute of Experimental and Clinical Medicine, Laboratory of Pharmacology, University of Ancona, 60100 Ancona (Italy). Key words : Glycine, Central analgesia, Peripheral analgesia Glycine (Gly) is one of the major inhibitory neurotrasmitters of CNS and its inhibitory actions are exerted on interneurons of the spinal cord and brainstem and on some neurons of higher centers. Recently (Rothman and O1ney, 1987), in many central areas Oly was shown to interact with an allosteric site of N-methyl-d-aspartate (NMDA) rece~tor, which is differentfrom the binding site from which Gly is displaced by strycnine, even if NMDA receptors are colocalized with the binding sites for sigma agonists. Besides, Gly has been reported to exert inhibitory effects on nociceptive ceils, thus mimicking the actions of morphine and of opioid peptides. Antagonistic and synergistic effects of morphine on the depressant action of Gly have been reported, but many data suggest that it is an effective agent in increasing acute morphine action and in attenuating the abstinence behaviour induced by morphine deprivation (Contrera and Tamayo, 1980). Few data are available about the CNS responses to Gly systemic administration that causes an increase of Gly central level. However, it remains to be proven if sir~ple augmentation of CNS G1y concentrations produces an enhancement of Gly-mediated inhibition. Similarly, certain metabolic disorders arise from a defect in Gly cleavage system which are characterized clinically by weakness and lethargy. 0031-6989/88/20S10057-2/$03.00/0 © 1988 The Italian Pharmacological Society