Effects of cholinergic receptor ligands on memory-related responses measured in the elevated plus maze test in mice

The aim of present experiments was to investigate the influence of cholinergic receptor’s ligands on memory-related behavior in mice, using the elevated plus maze (EPM) test. This test allows examining different processes of memory (acquisition and consolidation), depending on the time of drug treatment. The time necessary for mice to move from the opened arm to the enclosed arm (i.e. transfer latency, TL) was used as an index of memory. We revealed that in both processes of acquisition and consolidation, nicotine (0.035 and 0.175 mg/kg, free base, sc) shortened TL on the second day of experiment (TL2), improving memory processes. In contrast, scopolamine (0.3 and 1.0 mg/kg, ip) significantly increased TL2 values, impairing cognitive processes. In the following experiments, we evaluated the influence of a drug currently used in smoking cessation in humans, bupropion, on memoryrelated behavior induced by nicotine and scopolamine. Interestingly, the acute injection of bupropion (10 and 20 mg/ kg), prior to injections of both nicotine (0.035 mg/kg) or scopolamine (1.0 mg/kg), significantly prevented nicotine-induced memory improvement or scopolamine-induced memory impairment. Bupropion can diminish not only the rewarding (dependence-producing) effects of nicotine, but also its cognitive effects related to addiction. Our studies further indicated the great involvement of the cholinergic system in memory and allow development of more effective pharmacotherapies for memory impairment-like treatment of human disorders in which cholinergic pathways can be implicated.

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