Effects of ketamine on short-term memory avoidance response in rats

Purpose: The character of amnesia caused by ketamine was investigated at high and low subanesthetic dose levels in the rats. Methods: Rats were administrated ketamine (3, 10 mg kg-1) or serum physiologic (0.9% NaCl) intraperitoneally prior to learning and were tested after changes in locomotor activity have disappeared. An acquisition test was carried out immediately after learning by using a two compartment single trial passive avoidance paradigm for 180 s. Results: We showed that high subanesthetic dose of ketamine (10 mg kg-1) given prior to learning produced a significant decrease in acquisition latencies and percentage of animals without amnesia syndrome, but low subanesthetic dose (3 mg kg-1) had no effect on the acquisition of the passive avoidance responses. Conclusion: The results showed that short-term memory was impaired by high but not low subanesthetic dose of ketamine. Our findings suggest that amnesic effects of ketamine on short term memory might be related to the inhibition of NMDA receptors and activation of mesolimbic serotonergic transmission in the hippocampus