Acute scopolamine treatment decreases dopamine metabolism in rat hippocampus and frontal cortex.

The aim of the present study was to correlate the impairment of cognitive function induced by scopolamine with the activity of dopaminergic synapses in brain areas which are innervated by the mesocortical limbic system (e.g. hippocampus and frontal cortex) or by the mesostriatal system (e.g. striatum and nucleus accumbens). The results indicate that acetylcholine receptor blockade induced by the intraperitoneal injection of 0.5 mg/kg scopolamine resulted in a selective decrease in the content of the dopamine metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA). This effect appeared to be specific for the hippocampus and frontal cortex. Indeed, dopamine turnover in striatum and nucleus accumbens was not affected by scopolamine treatment. The scopolamine-induced decrease of dopamine turnover in both hippocampus and frontal cortex paralleled in terms of both time- and dose-dependence the drug-induced amnesic effects, as measured by a passive avoidance behavioral test.