DOPAMINE-RECEPTOR AGONIST POTENCIES FOR INHIBITION OF CELL FIRING CORRELATE WITH DOPAMINE D-3 RECEPTOR-BINDING AFFINITIES

The potencies for in vivo inhibition of substantia nigra pars compacta dopamine single cell firing were determined for apomorphine, BHT 920, N-0923, (+/-)-7-hydroxy-dipropylaminotetralin (7-OH-DPAT), (+)-3-(3-h ydroxyphenyl)-N-propylpiperidine (3-PPP), pramipexole, quinelorane, qu inpirole, RU 24926, U-86170, and U-91356. Significant correlation was obtained between the potencies of these 11 highly efficacious dopamine receptor agonists and the in vitro binding affinities at dopamine D-3 receptors, but not at dopamine D-2L receptors. These results support a functional role for the dopamine D-3 receptor subtype in the autorec eptor-mediated regulation of dopamine cell activity, while a role for dopamine D, receptors awaits further analysis. In addition, the result s demonstrate the limitations of using currently available dopamine re ceptor agonists to delineate relative in vivo roles for the dopamine D -2 and D-3 receptor subtypes.