Effects of medetomidine, a selective alpha 2-agonist, on position discrimination and reversal learning in aged rats.

The effect of a low dose (3 micrograms/kg) of medetomidine on cognitive performance of aged rats was examined in position discrimination and reversal learning in a T-maze. In Experiment 1, the reversal was introduced after 3 days of position habit acquisition and in Experiment 2 in the same session. Open-field and novelty-suppressed feeding tests were undertaken before drug testing to relate the cognitive effect of medetomidine with exploratory activity and neophobia of individual rats. Medetomidine slightly impaired the acquisition of position discrimination in both sexes and decreased perseveration in the reversal of a well-established position habit in females. The correlation of these findings with exploratory activity and neophobia is discussed.