In vitro effect of the racemic mixture and the (?)enantiomer of N-n-propyl-3-(3-hydroxyphenyl)-piperidine (3-PPP) on postsynaptic dopamine receptors and on a presynaptic dopamine autoreceptor

Publisher Website
Google Scholar
Abstract
The racemic mixture and the (−)enantiomer of the putative dopamine autoreceptor agonist 3-PPP were investigatedin vitro using dopaminesensitive adenylate cyclase in homogenates of rat striatum as a model for a postsynaptic D1-receptor type and inhibition of electrically-evoked tritium overflow from rat striatal slices preincubated with [3H]choline and [3H] dopamine as a model for a postsynaptic D2- and a presynaptic dopamine autoreceptor type, respectively. In contrast, to apomorphine, neither the racemic mixture nor the (−)enantiomer exerted any effect, suggesting agonistic properties in all three receptor models. However, both (±)3-PPP and (−)3-PPP were weak antagonists at postsynaptic D1- and D2-receptors. The results of the present investigation suggest that thein vivo effects of 3-PPP are either the result of metabolic activation or that this drug activates an other dopamine autoreceptor type, pharmacologically different from that one modulating doopamine release.