Modulation of mesolimbic dopamine release by the selective dopamine D3 receptor antagonist, (+)-S 14297

In Chinese hamster ovary cells stably transfected with recombinant rat dopamine D2 or D3 receptors, the naphthofurane antagonist, (+)-S 14297 [(+)-[7-(N,N-dipropylamino)-5,6,7,8-tetrahydro- naphtho(2,3b)dihydro,2,3-furane]], displayed a pronounced preference for dopamine D3 versus D2 receptors: Ki values = 13 and 365 nM, respectively. In contrast, its distomer, (-)-S 17777, showed low affinity (296 versus 3403 nM). The aminotetralin agonist, (+)-7-OH-DPAT (7-hydroxy-2-(di-n-propylamino)tetralin), also showed high affinity at dopamine D3 (1.8 nM) versus D2 (96 nM) receptors while its (-)-isomer showed low affinity (71 and 1461 nM). In freely moving rats, (+)-7-OH-DPAT (0.16 mg/kg s.c.)-but not (-)-7-OH-DPAT-decreased dialysate levels of dopamine in the nucleus accumbens. (+)-S 14297 (1.25 mg/kg s.c.) markedly inhibited the action of (+)-7-OH-DPAT without influencing dopamine levels alone. Further, this action was stereospecific in that (-)-S 17777 (20.0 mg/kg s.c.) was inactive. In conclusion, data obtained with the novel, selective dopamine D3 receptor antagonist, (+)-S 14297 suggest that dopamine D3 autoreceptors modulate the release of dopamine from mesolimbic dopaminergic neurones.