Oxotremorine- and atropine-induced changes of dopamine metabolism in the rat striatum

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Abstract
The effects of various doses of oxotremorine and of atropine (30 min, i.p.) on the metabolism of dopamine were examined in the striatum of the rat. Changes in striatal dopamine metabolism were estimated by following either the accumulation of [3H] dopamine 15 min after intravenous injection of [3H] tyrosine or the accumulation of dopa (taken as an index of dopamine synthesis) in animals pretreated with a dopa decarboxylase inhibitor Ro4–4602. Oxotremorine, 0·1 mg kg−1, and atropine, 1 mg kg−1, did not affect dopamine metabolism. Oxotremorine, 0·5 and 1·5 mg kg−1, did not modify dopamine concentrations but increased the accumulation of [3H]dopamine. The drug enhanced dopa formation in animals pretreated with Ro4–4602. Atropine, 5 and 20 mg kg−1, increased the accumulation of [3H]dopamine but did not affect dopamine concentrations. The accumulation of dopa was not modified there being no difference from the saline value in animals pretreated with the dopa decarboxylase inhibitor. Thus at high doses oxotremorine stimulated dopamine metabolism and atropine reduced dopamine utilization.