Benzodiazepines impair the acquisition and reversal of olfactory go/no-go discriminations in rats

The present study assessed whether benzodiazepines impair the acquisition, performance, and reversal of olfactory and auditory go/no-go discriminations in rats. Experiment 1 showed that midazolam (0.5-2 mg/kg sc) did not affect the performance of a well-learned two-odor olfactory discrimination and moderately facilitated performance of a go/no-go auditory discrimination. Experiment 2 found that midazolam (1 mg/kg) increased the number of errors made in the acquisition of a novel go/no-go olfactory discrimination task and in the reversal of a previously well-learned olfactory discrimination. However, midazolam did not affect the acquisition and reversal of an equivalent auditory discrimination task. Experiment 3 showed that diazepam (1 mg/kg) also impaired the acquisition and reversal of a novel olfactory discrimination task. Taken together, these results indicate that benzodiazepines cause a selective impairment of olfactory discrimination learning. This may reflect an effect of benzodiazepines in the glomerular circuitry of the olfactory bulb and at downstream olfactory processing sites such as the piriform cortex and orbitofrontal cortex.