3-PPP antagonizes the in vitro effects of D-1 and D-2 dopamine receptor agonists in rat neostriatum.

3-PPP has been reported to be a selective dopamine autoreceptor agonist, a conclusion based on in vivo studies. In rat neostriatum in vitro however, 3-PPP antagonized concentration-dependently the stimulation of cyclic AMP efflux caused by the D-1 receptor agonist SKF 38393 and the inhibition of K+-induced [3H]acetylcholine release caused by the D-2 receptor agonist LY 141865. 3-PPP alone did not affect [3H]acetylcholine release or cyclic AMP efflux. When interpreting the effects of 3-PPP in vivo dopamine receptor antagonism should be considered.