• glucocorticoid;
  • memory;
  • rat;
  • stress


Stress-related adrenal steroid hormones modulate brain and cognitive function. Electrophysiological studies, including primed burst potentiation and long-term potentiation, have indicated concentration-dependent inverted U-shape effects of corticosterone in hippocampal function and plasticity. Here, we explored the role of corticosterone in the consolidation and long-term retrieval of spatial learning in the Morris water maze task in rats. We postulated that corticosterone actions might be experience-dependent with regard to stimulus intensity, such as differential water temperatures. Indeed, rats trained at 19°C showed a quicker rate of acquisition and better long-term retention than rats trained at 25°C water. In addition, post-training corticosterone levels, on the first training day, were significantly higher in rats in the 19°C group than in the 25°C group. Performance of rats trained at 25°C, but not at 19°C, water was improved by injecting them i.p. with corticosterone immediately after each training session. Thus, the effect of exogenously administered corticosterone appears to be experience-dependent, with the experience-induced corticosterone concentrations as a critical factor determining the cognitive consequences of steroid treatment. Therefore, this work indicates a facilitating corticosterone action, during the post-training period, on the neural mechanisms determining the strength of information storage under acute, physiological conditions.