Effects of anticholinergic drugs and medial septum lesion on short-term memory for visual and auditory stimuli in rats.

Abstract

This study examined the effects of administration of anticholinergic drugs and medial septum lesion on the performance of the successive delayed matching-to-sample (S-DMTS) task in rats in order to clarify the relationship between the central cholinergic system and the modality effect in rats' short-term memory. A pair of visual and/or auditory stimuli was presented with delay intervals to rats. They were required to distinguish whether the modality of the 2nd stimulus (S2) for the pair was the identical to or different from that of the 1st stimulus (S1). Scopolamine at 0.03-0.1mg/kg (i. p.) and mecamylamine at 1-3mg/kg (i. p.) disrupted the performance of S-DMTS task irrespective of the modality of S1, whereas methyl-scopolamine and hexamethonium did not. These results suggest that muscarinic and nicotinic receptors in rats' brain are correlated with short-term memory for both visual and auditory stimuli. Lesion to medial septum also disrupted the performance of S-DMTS task when the visual stimulus was presented as S1, however, the performance was not changed when the auditory stimulus was employed. These findings suggest that the medial septum is correlated with the mnemonic processes of visual but not of auditory stimuli.View full abstract