[Influence of nicotine on muscimol state-dependent memory in the step-down passive avoidance test]

ABSTRACT

Due to overlapping distribution of GABA receptors with nicotinic receptors in some parts of brain such as dorsal hippocampus, the functional interactions between nicotinic acetylcholine and GABA ergic systems in cognitive control seems possible. The present study evaluated the possible role of nicotinic receptors of the dorsal hippocampus in muscimol [the GABA[A] receptor agonist] induced amnesia and muscimol state-dependent memory in adult male mice. This experimental study included 185 adult male NMRI mice. The drugs used in this study were muscimol and nicotine. The mice were anaesthetized and placed into a stereotaxic apparatus. Cannulas were implanted bilaterally in the CA1 regions of the dorsal hippocampus. After a seven day recovery period, the behavioral testing was performed by using inhibitory avoidance task. Prolongation of the step-down latency was measured as a criterion for the assessment of memory retention. Post-training administration of muscimol [0.15 and 0.075 micro g/mouse] decreased the memory retrieval. The memory impairment induced by muscimol [0.15micro g/mouse] was completely reversed by administration of muscimol or nicotine [1.5 and 1 micro g/mouse] on the test day, which suggests muscimol, induced state-dependent memory. These results suggested that nicotinic receptors of the dorsal hippocampus may play an important role in muscimol -induced amnesia and muscimol state-dependent memory