Short- and Long-Term Treatments with Dexamethasone have Different Effects on Spatial Learning and Memory

Dexamethasone (DEX) to promote an increase in levels of corticosterone, the hormone that initiates stressful responses. We analyzed the effect of DEX on spatial learning and memory (Morris water maze) in young male Sprague-Dawley rats. We administered two different treatment regimens of daily 0.2 mg/kg DEX as independent variable. One treatment consisted of DEX treatment for 5 days, and the second consisted of DEX treatment for 14 days. The short-term treatment promoted improved spatial learning without any effects on memory. The long-term treatment caused deficits in spatial learning and memory. We also observed that a Control group (CON) treated for 14 days with a vehicle (SSI: 0.9% saline solution) was more efficient in the test compared with a control group that was treated for 5 days with SSI. These results show that simply the time of exposure to stressful stimuli as injection, can cause changes in the Morris water maze execution.