Dopamine release in the nucleus accumbens of freely moving rats determined by on-line dialysis:Effects of apomorphine and the neuroleptic-like peptide desenkephalin-γ-endorphin

This study examined the effects of apomorphine, sulpiride, desenkephalin-γ-endorphin (DEγE) and a combination of DEγE with apomorphine on the release of dopamine (DA) and its main metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the nucleus accumbens of freely moving rats. A fully automated on-line brain dialysis system was used. A small dose of s.c. administered apomorphine induced a decrease in the output of DA and DOPAC. Sulpiride, infused into the nucleus accumbens, induced a 2-fold increase in the output of DA, DOPAC and HVA. DEγE hardly modified either the basal release of DA, DOPAC and HVA or the apomorphine-induced attenuation of the release of DA and DOPAC. These results indicate a dissociation between the behavioural effects of DEγE and its effect on the release of DA in vivo