Figure 4.

Chronic CORT induces multiple olfactory deficits most of which are restored by FLX. A, Go/no-go procedure. In response to a positive odor stimulus (S⁺), the trained mouse licks the water port to receive the water reward. B, Graph showing the mean percentage of correct responses in each block of the discrimination task between 1% IAA and 1% MO. All groups of mice reached criterion performance, which corresponds to 90% of correct responses in at least one block. A score of 50% corresponds to the success rate at chance level. C, Graph depicting the mean percentage of correct responses in each block of the discrimination task between two carvone enantiomers and their mixtures. To further evaluate olfactory discrimination, we trained mice to discriminate mixtures of increasing complexity. Mice were first trained to distinguish 1% carvone⁺ and 1% carvone⁻. Once mice reached this criterion, they were subjected to the more difficult task of mixture discrimination. The mixture ratio of carvone⁺ and carvone⁻ is indicated on the graph. All groups showed similar performance in the simple discrimination task of carvone⁺ versus carvone⁻. However, the ability to discriminate between carvone mixtures was reduced by CORT and not restored by FLX. D, CORT-treated mice required significantly higher concentrations of N-butanol for odorant detection compared with vehicle-treated and CORT+FLX-treated animals. E, To assess olfactory memory, mice were trained during 5 consecutive days to recall distinguishing carvone⁺ and carvone⁻. Mice were then retested in the simple carvone discrimination task at 30 d (t30) following the end of the training session (t0). CORT-treated animals exhibited a memory deficit that was attenuated by FLX. Values are plotted as mean ± SEM (n = 8 for vehicle and CORT-treated; n = 35 for CORT+FLX). *p < 0.05, **p < 0.01.