A comparison of the effects of the dopamine partial agonists aripiprazole and (−)-3-PPP with quinpirole on stimulated dopamine release in the rat striatum: Studies using fast cyclic voltammetry in vitro

The effects of aripiprazole, (−)-(3-hydroxyphenyl)-N-n-propylpiperidine ((−)-3-PPP) and quinpirole on single and multiple pulse stimulated dopamine release were investigated using the technique of fast cyclic voltammetry (FCV) in isolated rat striatal slices. Aripiprazole and (−)-3-PPP had no significant effect on single pulse dopamine release at concentrations from 10 nM to 10 μM indicating low agonist activity. The compounds failed to potentiate 5 pulse stimulated release of dopamine although inhibitory effects were seen at 10 μM for aripiprazole. Both compounds were tested against the concentration-response curve for quinpirole's inhibition of stimulated single pulse dopamine release. Aripiprazole and (−)-3-PPP shifted the concentration-response curve for quinpirole to the right. In each case this was greater than a 100-fold shift for the 10 μM test compound. Whilst these results indicate that both compounds show little agonist activity on dopamine release and significant antagonism of the inhibitory effect of quinpirole on dopamine release, whether they are functionally selective dopamine D2 ligands remains controversial.