One-trial tolerance to the effects of chlordiazepoxide in the elevated plus-maze is not due to acquisition of a phobic avoidance of open arms during initial exposure.
Author(s): Frussa-Filho R, Ribeiro Rde A
Affiliation(s): Departamento de Farmacologia, Escola Paulista de Medicina, Universidade Federal de Sao Paulo, Rua Botucatu 862, Edificio Jose Leal Prado, CEP 04023-062, SP, Sao Paulo, Brazil. email@example.com
Publication date & source: 2002-06-21, Life Sci., 71(5):519-25.
A single exposure to the elevated plus-maze (EPM) test of anxiety reduces or abolishes the anxiolytic-like efficacy of benzodiazepines. This phenomenon called one-trial tolerance has been suggested to represent the acquisition of a phobic-like response to the open arms during trial 1. The present study was designed to examine the effects of chlordiazepoxide (5 mg/kg, ip) on the behaviour of rats in a conventional EPM apparatus after previous exposure to a four-open-arm EPM, a four-enclosed arm EPM or a conventional EPM, as well as in naive rats. Chlordiazepoxide had clear-cut anxiolytic-like effects (increased percentage of time spent on the open arms) in a traditional EPM in naive rats and in animals previously exposed to a four-open-arm EPM. However, it was ineffective in rats previously exposed to a traditional or a four-closed-arm EPM. Thus, the phenomenon of one-trial tolerance does not depend upon initial open-arm experience.