title: An approach to evaluate the ability of rats to discriminate different levels of illumination in the plus maze test: effects of scopolamine.
abstract: Previous research has shown that the visual system is important for rats to establish the arm preference in the elevated plus maze (EPM), an animal model of anxiety. This study aims at evaluating whether a gradient of illumination between the enclosed arms of the maze (E/E(DeltaLux)) could be a reliable approach to detect drugs-induced harmful effect on visual discrimination of rats. Four EPM configurations with different E/E(DeltaLux) (8, 41 and 85lx) were used to demonstrate that as E/E(DeltaLux) increases, rats avoid to explore the light enclosed arm, which characterizes the animal ability to discriminate the most illuminated area within the protected environment of the maze. The establishment of either 41 or 85 E/E(DeltaLux) failed to alter the traditional spatial-temporal variables in the EPM. In addition, systemic treatment with midazolam (MDZ; 1.0mgkg(-1), a classical anxiolytic) induced anxiolysis in rats tested in 41 and 85 E/E(DeltaLux) EPM, with no change in the visual discrimination, when evaluated by the level of light enclosed arm exploration. Systemic treatment with scopolamine (SCP; 1.0, 2.0 and 8.0mgkg(-1)), a drug endowed with harmful properties upon the visual system, did not change either the open arm avoidance or the visual discrimination at the low doses, but induced increased light enclosed arm (visual discrimination deficit) and open arm exploration (anxiolytic like effect) at a higher dose. We propose that the incorporation of an E/E(DeltaLux) in the EPM may reinforce the predict validity of the test since it enables to evaluate whether a visual discrimination deficit can be confounded with an anxiolytic-like effect, thus establishing a false positive detection.
authors.affiliation: Department of Physiological Sciences, Centre of Biological Sciences, Federal University of Santa Catarina, 88.040-900 Florianópolis, SC, Brazil.
authors.forename: Marcos Aurélio
authors.initials: MA
authors.lastname: de Araújo Godinho
authors.forename: Luana
authors.initials: L
authors.lastname: Meneghini
authors.forename: Aparecida Marcia
authors.initials: AM
authors.lastname: Lucinda
authors.forename: Fábio Rodrigo Mesquita
authors.initials: FR
authors.lastname: Borges
authors.forename: Diana Yae
authors.initials: DY
authors.lastname: Sakae
authors.forename: José
authors.initials: J
authors.lastname: Marino Neto
authors.forename: Marta Aparecida
authors.initials: MA
authors.lastname: Paschoalini
authors.forename: Thereza Christina Monteiro
authors.initials: TC
authors.lastname: de Lima
authors.forename: Moacir Serralvo
authors.initials: MS
authors.lastname: Faria
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D014151:Anti-Anxiety Agents / Q000008:administration & dosage*; D001007:Anxiety / Q000188:drug therapy; D001245:Association Learning / Q000187:drug effects; D001362:Avoidance Learning / Q000187:drug effects*; D004193:Discrimination Learning / Q000187:drug effects*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005106:Exploratory Behavior / Q000187:drug effects; D008029:Lighting; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D012601:Scopolamine / Q000008:administration & dosage*; D018709:Statistics, Nonparametric; D014786:Vision Disorders / Q000139:chemically induced / Q000175:diagnosis; D014796:Visual Perception / Q000187:drug effects*
chemical_list: D014151:Anti-Anxiety Agents; D012601:Scopolamine