Figure 4
(a) Effects of glucocorticoid receptor (GR) antagonist (RU-38486 or mifepristone) and mineralocorticoid receptor (MR) antagonist (RU-28318) on delayed alternation rates. Both antagonists were injected bilaterally in the dorsal hippocampus at the dose of 20 μg/ml each 15 min before behavioral testing. Control groups were either non-operated animals or animals receiving vehicle only. The administration of both antagonists did not significantly modify alternation rates as compared to control groups. Chance level: 50%. (b) Effects of GR antagonist (RU-38486 or mifepristone) and MR antagonist (RU-28318) and Cort–3CMO–BSA (corticosterone–3-O-carboxymethyloxime–BSA conjugate) on delayed alternation rates. Both antagonists were injected bilaterally in the dorsal hippocampus at the dose of 50 ng/ml each 15 min before the Cort–3CMO–BSA injection (1 mg/ml). Behavioral testing occurred 15 min after Cort–3CMO–BSA injection. Control groups were either animals receiving two vehicle injections separated by 15 min or animals receiving vehicle, followed 15 min later by Cort–3CMO–BSA injection. Results showed that the MR antagonist blocked the memory impairment observed in animals receiving Cort–3CMO–BSA only; in contrast, the GR antagonist did not block the deleterious effects of Cort–3CMO–BSA injection on alternation rates. Comparisons to Cort–3CMO–BSA-treated animals: *p<0.05; **p<0.01; chance level: 50%.
