Microdialysis and striatal dopamine release: stereoselective actions of the enantiomers of N-0437

An intracerebral dialysis method was used to test both enantiomers of the very potent and selective dopamine (DA) D-2 agonist 2-(N-propyl-N-2-thienylethylamino)-5-hydroxytetralin, N-0437, for their actions on DA receptors in the striatum of the rat. (-)N-0437 induced a 60% decrease in DA release, which was independent of the presence or absence of a kainic acid lesion placed unilaterally in the striatum. Stereotyped behaviour was apparent following administration of the (-) enantiomer. Thus, (-)N-0437 displayed an agonistic action on both pre- and postsynaptic D-2 receptors. (+)N-0437 did not induce any effect in the release model after peripheral administration nor did it induce any form of stereotypy. A comparison between the effects of (-)N-0437 after oral (10 mumol/kg) and transdermal (10 mumol/kg) administration showed the advantages of the latter mode of administration. Transdermal application induced a much longer duration of action of the drug (13 h) in comparison with the oral mode (5 h). Thus, transdermal administration may be a very useful method of drug application for therapeutic use.