title: Infusion of galanin into the mid-caudal portion of the dorsal raphe nucleus has an anxiolytic effect on rats in the elevated T-maze.
abstract: Galanin and 5-HT coexist in dorsal raphe nucleus (DRN) neurons. Microinjection of galanin into the DRN reduces the firing rate of serotonin neurons. Serotonergic neurons projecting from the DRN to the amygdala facilitate learned anxiety producing an anxiogenic effect, while those projecting from the periaqueductal grey affect innate anxiety producing a panicolytic effect. We tested the hypothesis that injection of galanin into rat DRN would induce anxiolytic/panicogenic effects in the elevated T-maze (ETM), a model that allows for the evaluation of both of these effects. Galanin infusion into the mid-caudal DRN, but not into the rostral DRN, impaired inhibitory avoidance, suggesting an anxiolytic effect. The effective dose of galanin (0.3 nmol) did not modify locomotor activity in the open field. Contrary to expectations, microinjection of galanin into the DRN did not facilitate the latency of one-way escape in the ETM. Pretreatment with a galanin antagonist, M40, attenuated galanin-induced impairment of inhibitory avoidance. The results show that microinjection of a low dose of galanin only into the mid-caudal DRN has an anxiolytic effect. This effect seems to be mediated, at least in part, by galanin receptors. Further investigation is necessary to identify the receptor subtypes and the DRN subregion involved in the anxiolytic effect of galanin.
authors.affiliation: Department of Pharmaceutical Sciences, Health Science Center, Federal University of Espirito Santo, Vitoria, ES 29043-900, Brazil.
authors.forename: Gabriela Pandini
authors.initials: GP
authors.lastname: Silote
authors.forename: Aline Boroto
authors.initials: AB
authors.lastname: Rosal
authors.forename: Mayara Machado
authors.initials: MM
authors.lastname: de Souza
authors.forename: Vanessa
authors.initials: V
authors.lastname: Beijamini
mesh_terms: D000704:Analysis of Variance; 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; D004924:Escape Reaction / Q000187:drug effects; D019004:Galanin / Q000494:pharmacology / Q000627:therapeutic use*; D008297:Male; D018782:Maze Learning / Q000187:drug effects* / Q000502:physiology; D009043:Motor Activity / Q000187:drug effects; D011903:Raphe Nuclei / Q000187:drug effects* / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D014151:Anti-Anxiety Agents; D019004:Galanin
keywords: Anxiety; Dorsal raphe nucleus; Elevated T-maze; Galanin