Scopolamine-induced hypermotility in rats is mediated via a dopaminergic system

To clarify the relation between cholinergic and dopaminergic transmission systems involved in locomotor effects the influence of dopaminergic drugs on scopolamine hypermotility was investigated. Scopolamine and apomorphine in locomotor stimulant doses showed additive effects. Apomorphine in a dose acting on presynaptic dopaminergic receptors decreased the scopolamine hypermotility markedly. Haloperidol antagonized both scopolamine and apomorphine hypermotility in an apparently competitive way. Sulpiride potentiated scopolamine locomotor effect. Additionally, it was shown that LSD potentiated scopolamine hypermotility as well as apomorphine hypermotility. The results suggest in connection with literature data that locomotor effects of drugs affecting cholinergic transmission may by mediated by a dopaminergic system.