Effects of atropine on avoidance condition: Interaction with nicotine and comparison with N-methyl-atropine.

Atropine, when given to rats shortly before acquisition of a conditioned avoidance response, increases the number of correct responses both in that session and in a retention session performed 5 days later; when the drug is given at a longer pre-trial interval, it has, instead, a depressant action. The depressant action is not observed when the performance of a previously well established conditioned response is measured, instead of the acquisition of a new one. Furthermore, the depressant action does not seem to interfere with the previously reported enhancing action of post-trial atropine on memory consolidation. It does, however, block the enhancing effects of nicotine on learning. The stimulant effect of atropine at short pre-trial intervals is mimicked by N-methyl-atropine at moderate doses; the depressant effect of atropine is shared by high doses of the N-methylated analog. The effects of N-methyl-atropine are not time-dependent, as those of the parent compound. [ABSTRACT FROM AUTHOR]