Preference for the light compartment of a light/dark cage does not affect rat exploratory behavior in the elevated plus-maze.

Andrea Milena Becerra Garcia,Silvio Morato,Raquel Chacon Ruiz Martinez

doi:10.3922/j.psns.2008.1.012

Abstract

The are few reports on the relationship between elevated plus-maze and effects of maintenance conditions in the days prior to the test. Previously, we have demonstrated that being forcibly in total dark or in light for four days does not alter exploratory behavior in the plus-maze. The present study aimed at recording illumination level preferences in rats using a box with light and dark compartments (or another with two light compartments) and the behavioral effect of this choice on the plus-maze. The rats allowed to express their preference to remain in one particular level of illumination tended to stay initially in the dark compartment and gradually preferred to remain in the light compartment. When tested in the elevated plus-maze there were no effects in comparison to controls kept in commercial cages.

Highlights

The elevated plus-maze, a modification inspired in a procedure introduced almost five decades ago by Montgomery (1955), was first reported by Handley & Mithani (1984) and has often been used to investigate anxiolytic and anxiogenic compounds and to study the involvement of neurotransmitters in anxiety (e.g., Pellow & File, 1986; Moser, 1989; Cruz, Frei & Graeff, 1994; Rodgers & Cole, 1994)
Related to the test situation is the presence of raised edges surrounding the open arms, which prevent the rats from falling (Treit et al, 1993; Fernandez & File, 1996; Cardenas et al, 2001), manipulation of experimental subjects, such as the way rats are transported to the test room (Morato & Brandão, 1996), whether they are housed in groups or individually (Maisonnette, Morato, & Brandão, 1993) or the place and how long they are kept there before testing (Morato & Brandão, 1997)
As far as the conventional anxiety measures — entries and time spent in open arms and their extremities — are concerned (Pellow, Chopin, File, & Briley, 1985; Cruz et al, 1994), the groups housed in the different cages did not differ in terms of exploratory behavior in the elevated plus maze, in comparison to control rats kept in commercial cages

Summary

Introduction

The elevated plus-maze, a modification inspired in a procedure introduced almost five decades ago by Montgomery (1955), was first reported by Handley & Mithani (1984) and has often been used to investigate anxiolytic and anxiogenic compounds and to study the involvement of neurotransmitters in anxiety (e.g., Pellow & File,, 1986; Moser, 1989; Cruz, Frei & Graeff, 1994; Rodgers & Cole, 1994). Still others concern the test situation itself, such as the levels of illumination of the test room (Gentsch Lichtsteiner, Kraeuchi, & Feer, 1982; Morato & Castrechini, 1989; Griebel et al, 1993; Cardenas, Lamprea, & Morato, 2001; Garcia, Cardenas, & Morato, 2005). These studies indicate that exploration of the open arms is increased by low levels of environmental illumination. Related to the test situation is the presence of raised edges surrounding the open arms, which prevent the rats from falling (Treit et al, 1993; Fernandez & File, 1996; Cardenas et al, 2001), manipulation of experimental subjects, such as the way rats are transported to the test room (Morato & Brandão, 1996), whether they are housed in groups or individually (Maisonnette, Morato, & Brandão, 1993) or the place and how long they are kept there before testing (Morato & Brandão, 1997)

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Conclusion