Effects of context in crossed to lerance diazepamethanol in the elevat ed plus-maze (ETM)

Abstract

Tolerance is stronger when the drug is administrated in the context that signals the presence of the drug. This study was designed to evaluate the effect of context on development of tolerance to diazepam and cross tolerance diazepam- ethanol, on exploratory activity in the elevated plus maze (EPM) and in motor activity. Male Wistar rats were assigned to independent groups (n =8). In Experiment 1, the effect of acute administration of ethanol (1.5 mg/kg) and diazepam (1mg/kg) was evaluated. In Experiment 2, the effect of context was evaluated on the development of tolerance: two chronic groups received 20 administrations of diazepam in different contexts, one in the Colony Room context and other in the Laboratory context, the Control group received 21 administration of saline in equivalent volume (1ml/kg) in the Laboratory context; on test day all groups were evaluated in the Laboratory context. In Experiment 3, following the same procedure, the effect of context was evaluated on the development of cross tolerance diazepam-ethanol. Immediately after exposure on the ETM, motor activity was evaluated in all groups. Diazepam and ethanol produced anxiolysis (Experiment 1); the chronic groups developed tolerance independently of the context, although it was stronger in the context associated with the drug (Experiment 2). In Experiment 3, the development of cross-tolerance diazepam-ethanol and the effect of context were observed.