Contextual control over the expression of fear in rats conditioned under abenzodiazepine

Rationale: Benzodiazepines disrupt fear conditioning, but this disruption i s context-specific: if rats have been conditioned under a benzodiazepine, t heir fear is recovered if they are tested in a different context. The prese nt experiments investigated how the conditioning context controls fear in r ats conditioned under a benzodiazepine. Objectives: The experiments had thr ee aims: (I) to replicate the finding that fear is recovered when rats are tested in a different context, (2) to test whether the conditioning context reduces fear generally or only for the specific stimulus conditioned in th at context and (3) to test whether latent inhibition of the conditioning co ntext reduces its control over fear. Methods: Rats were injected with the b enzodiazepine midazolam (1.25 mg/kg) or saline and exposed to a conditioned stimulus (CS) and shock in a distinctive chamber. Latent inhibition of the chamber was induced by extensively preexposing the rats to the chamber. Th e day after conditioning, fear was assessed by presenting the CS while rats were in either the conditioning chamber or a different chamber. Results: T he midazolam-induced reduction of fear was reversed (i.e. fear was partiall y recovered) if rats were tested in the different context, and was complete ly prevented if the conditioning context had been latently inhibited. These two effects were not additive since, when the conditioning context had bee n latently inhibited, rats showed less fear in the different context than i n the conditioning context. Conclusions: We argue that midazolam does not d isrupt conditioning, but imbues the conditioning context with control over retrieval of the CS-shock association. In this regard, the effects of midaz olam closely parallel those of extinction.