Previous studies have indicated that memory retrieval is impaired under high levels of blood glucocorticoids as seem in severe stress. In this study, we investigated the effect of peripheral injection of metyrapone (an inhibitor of glucocorticoid synthesis) on memory retrieval in rats.

Forty young rats were trained in a passive avoidance task. Retention test was done 48hr after training. Metyrapone (25, 50 and 100 mg/kg) or vehicle was injection IP 90 min before of retention test. Memory retention of each animal was measured as latency time to enter the dark chamber of the task.

The results showed that administration of metyrapone at doses of 25 and 100 mg significantly impaired memory retrieval as compared with control group. No significant effect was found with intermediate dose of metyrapone (50 mg/kg).

These findings provide evidence that inhibition of glucocorticoid synthesis by metyrapone impair memory retrieval in a U shape manner. Further study are required the specificity of observed effects of metyrapone.

Key words: 

glucocorticoids, metyrapone, memory retrieval, passive avoidance task