title: Galanin microinjection into the dorsal periaqueductal gray matter produces paradigm-dependent anxiolytic effects.
abstract: Galanin is a peptide that is present in the central nervous system in mammals, including rodents and humans. The actions of galanin are mediated by three types of metabotropic receptors: GAL1, GAL2, and GAL3. GAL1 and GAL3 increase K(+) efflux, and GAL2 increases intracellular Ca(2+) levels. The distribution of galanin and its receptors suggests its involvement in fear and/or anxiety. The periaqueductal gray matter (PAG) is a key mediator of defensive behaviors that is both targeted by galaninergic projections and supplied with GAL1 receptors and, less markedly, GAL2 receptors. We examined the effects of galanin microinjections in the dorsal PAG (dPAG) on the performance of rats in different models of anxiety. Male Wistar rats (n=7-12) were implanted with guide cannulae in the dPAG. They received microinjections of either galanin (0.3, 1.0, and 3.0 nmol) or vehicle and were tested in the Vogel conflict test (VCT), elevated plus maze (EPM), and elevated T-maze (ETM). Rats that were tested in the ETM were further evaluated for exploratory activity in the open field test (OFT). Galanin microinjections had no effects on anxiety-like behavior in the EPM or VCT or exploratory activity in the EPM or OFT. In the ETM, however, microinjections of 3 nmol galanin impaired learned anxiety (i.e., avoidance of the open arms) without changing unconditioned fear (i.e., escape from the open arms). The present data suggest that galanin transmission in the dPAG inhibits the acquisition of anxiety-like responses in the ETM.
authors.affiliation: Biochemistry and Pharmacology Postgraduate Program, Health Science Center, Federal University of Espirito Santo, Vitoria, ES 29043-900, Brazil.
authors.forename: F R C
authors.initials: FR
authors.lastname: Soares
authors.affiliation: Biochemistry and Pharmacology Postgraduate Program, Health Science Center, Federal University of Espirito Santo, Vitoria, ES 29043-900, Brazil.
authors.forename: G P
authors.initials: GP
authors.lastname: Silote
authors.affiliation: Department of Pharmacology, Federal University of Minas Gerais, Belo Horizonte, MG 31270-901, Brazil.
authors.forename: A F
authors.initials: AF
authors.lastname: Almeida-Santos
authors.affiliation: Department of Pharmacology, Federal University of Minas Gerais, Belo Horizonte, MG 31270-901, Brazil.
authors.forename: D C
authors.initials: DC
authors.lastname: Aguiar
authors.affiliation: Biochemistry and Pharmacology Postgraduate Program, Health Science Center, Federal University of Espirito Santo, Vitoria, ES 29043-900, Brazil.
authors.forename: L C
authors.initials: LC
authors.lastname: Schenberg
authors.affiliation: Biochemistry and Pharmacology Postgraduate Program, Health Science Center, Federal University of Espirito Santo, Vitoria, ES 29043-900, Brazil. Electronic address: vanessabh77@gmail.com.
authors.forename: V
authors.initials: V
authors.lastname: Beijamini
mesh_terms: D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology / Q000627:therapeutic use; D001007:Anxiety / Q000188:drug therapy*; D001362:Avoidance Learning / Q000187:drug effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005106:Exploratory Behavior / Q000187:drug effects; D019004:Galanin / Q000494:pharmacology* / Q000627:therapeutic use*; D008297:Male; D008845:Microinjections; D010487:Periaqueductal Gray / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018709:Statistics, Nonparametric
chemical_list: D014151:Anti-Anxiety Agents; D019004:Galanin
keywords: Anxiety; Elevated T-maze; Elevated plus maze; Galanin; PAG; Vogel conflict test