Two opposite effects of diazepam on fear by differential training in the CER-paradigm.

Two groups of rats were trained in a CER paradigm. The conditioned stimulus was a sound, the unconditioned stimulus was an electric shock. Group 1 received conventional CER training before the effects of different doses of diazepam were studied. For Group 2 the shock was always and exclusively given contingent on pretreatment with diazepam. After prolonged training the compound thus became a discriminative stimulus complex (DSC) and produced response suppression during the CS. Group 2 was also challenged with various doses of diazepam. The results showed that diazepam acquired diametrically different properties in the two groups. Group 1 exhibited disinhibitory effects and Group 2 suppressive effects, which may reflect anxiolytic and anxiogenic properties, respectively.