Scopolamine differentially affects memory of 8- and 16-month-old rats in the double Y-maze

The present study investigated the effects of scopolamine on working and reference memory in the same rats at 8 and 16 months of age. Rats were trained in the double Y-maze until a criterion of greater-or-equal, slanted88% correct was reached on both memory components. Doses of scopolamine (0.1, 0.4, 0.8 mg/kg for rats at 8 months; 0.05, 0.1, 0.4 mg/kg for rats at 16 months) were administered in a counterbalanced order 30 min before test sessions which also included delays of 0, 5, or 30 s prior to both memory components. Results showed that at both ages the 0.1 mg/kg scopolamine dose selectively impaired working memory, whereas higher doses impaired both working and reference memory. Delays selectively decreased working memory choice accuracy and enhanced the effect of scopolamine. Rats at 16 months performed less well on both reference and working memory and showed greater impairments with scopolamine and delays. The present findings support the hypothesis that a decrease in cholinergic neurotransmission contributes to age-related memory deficits.