LASTING EFFECTS OF DOPAMINE-RECEPTOR AGONISTS UPON STRIATAL DOPAMINE RELEASE IN FREE-MOVING RATS - AN IN-VIVO VOLTAMMETRIC STUDY

It is now well known that dopamine (DA) receptors agonists can reduce striatal DA release. These compounds are generally thought to produce short-term effects. However, in a recent in vivo study we have reported that the D-1/D-2 receptor agonist apomorphine might induce decrements in striatal DA release that lasted several hours. In order to establish whether the effect of apomorphine was idiosyncratic or extended to other DA receptor agonists, we have investigated the effects of the selective D-1 receptor agonist SKF 38393 and of the selective D-2 receptor agonist LY 171555 upon striatal DA release using differential pulse voltammetry and multi-fibre carbon electrodes selective for DA. Results support that these DA receptor agonists can reduce DA release for several hours. The effects of SKF 38393 and of LY 171555 would be DA receptor-mediated since they can be blocked by the selective D-1 receptor antagonist SCH 23390 and the selective D-2 receptor antagonist sulpiride respectively. These findings are discussed at the light of current literature including methodological and biological data.