The Involvement of Catecholamine in Scopolamine-Induced Locomotor Activation and Rotational Behaviour in Mice

Abstract

Scopolamine-induced locomotor activation was studied in comparison with the responses to apomorphine and methamphetamine in mice. The responses to scopolamine and methamphetamine were markedly depressed by the pretreatment with the catecholamine synthesis inhibitor, .alpha.-methyl-p-tyrosine, while the activation response to apomorphine was not affected. p-Chlorophenylalanine did not affect the response to scopolamine. Phenoxybenzamine reduced the responses to scopolamine and methamphetamine, but did not affect the apomorphine response. Propranolol did not affect the responses to the 3 agonists, scopolamine, apomorphine and methamphetamine. Antipsychotic drugs haloperidol and pimozide reduced the responses to the 3 agonists. Haloperidol was especially effective in this regard. The involvement of catecholamine in the locomotor activation produced by scopolamine was suggested. In the rotational behavior model which is sensitive to dopamine receptor stimulating agents, effects of the 3 agonists were studied. Scopolamine produced the ipsilateral rotation in mice with unilateral striatal 6-hydroxy-dopamine-induced lesions. Methamphetamine induced the ipsilateral rotation, while apomorphine produced the contralateral rotation. The rotations induced by 3 agonists were suppressed by pimozide. The participation of dopamine in the scopolamine-induced rotational behavior in mice was suggested.