title: Activation of dorsal periaqueductal gray by glycine produces long lasting hyponociception in rats without overt defensive behaviors.
abstract: Electrical or glutamate stimulation of the dorsal periaqueductal gray matter (DPAG) of rats induces overt defensive behavior, such as freezing or flight, and hyponociception, while glycine and D-serine, a specific NMDA/GLY(B)-site ligand, produced only subtle defensive behavior related to risk assessment and avoidance from the open arms in the elevated plus-maze test. In order to verify whether the GLY(B) site in the DPAG could also be involved in hyponociception, glycine (GLY; 10, 20, 50, and 80 nmol/0.3 microl) and (+/-)-3-amino-1-hydroxy-2-pyrrolidone (HA966; 10 nmol/0.3 microl), a GLY(B)-site antagonist, were microinjected in rats submitted to the radiant heat-induced tail-flick test. GLY increased tail-flick latencies in a dose-dependent way. This hyponociceptive effect was completely reversed by co-administration with HA966. GLY given in the deep layer of superior colliculus did not produce changes in tail-flick latencies. Therefore, the results suggest that the activation of GLY(B) receptors in the DPAG is also involved in the hyponociception elicited by this brain area.
authors.affiliation: Department of Pharmacology, Federal University of Santa Catarina, Florianópolis, SC, Brazil.
authors.forename: M A
authors.initials: MA
authors.lastname: Martins
authors.forename: A P
authors.initials: AP
authors.lastname: Carobrez
authors.forename: C R
authors.initials: CR
authors.lastname: Tonussi
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005998:Glycine / Q000494:pharmacology*; D008024:Ligands; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D008845:Microinjections; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects*; D010487:Periaqueductal Gray / Q000378:metabolism / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018009:Receptors, Glycine / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D013997:Time Factors
chemical_list: D008024:Ligands; D018009:Receptors, Glycine; D016194:Receptors, N-Methyl-D-Aspartate; D005998:Glycine