The enantiomers of SK&F 83566, a new selective D-1 dopamine antagonist, stereospecifically block stereotyped behaviour induced by apomorphine and by the selective D-2 agonist RU 24213.

The non-selective dopamine receptor agonist apomorphine and the selective D-2 receptor agonist RU24213 each induced a typical syndrome of stereotyped behaviour characterised by sniffing and locomotion. The syndrome and its associated behaviours induced by each agonist were dose-dependently antagonised by pretreatment with the R- but not with the S-enantiomer of the benzazepine SK&F 83566. R- but not S-SK&F 83566 stereoselectively blocks D-1 receptors with high affinity, while the enantiomers have a very weak affinity for D-2 receptors which shows negligible stereoselectivity. Therefore, enantioselective blockade of brain D-1 receptors appears able to influence the expression of behaviours initiated by D-2 receptor stimulation.