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 |
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Authors: | Frussa-Filho R Ribeiro R de A |
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Institution: | Departamento de Farmacologia, Escola Paulista de Medicina, Universidade Federal de S?o Paulo, Rua Botucatu 862, Edifício José Leal Prado, CEP 04023-062, SP, S?o Paulo, Brazil. rosanari@terra.com.br |
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Abstract: | 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. |
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Keywords: | Chlordiazepoxide Elevated plus-maze Tolerance Anxiety Phobia |
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