Dopamine denervation of the nucleus accumbens induces a selective increase in the number of delta-opioid binding sites.

Selective lesions of dopamine (DA) neurons of the nucleus accumbens were made in rats by local injections of 6-hydroxydopamine (6-OHDA). Seven days after 6-OHDA, the binding affinities and capacities at mu-, delta- and kappa-opioid binding sites were determined in the nucleus accumbens by selective labelling techniques. 6-OHDA pretreatment caused a significant increase in the number of delta-opioid binding sites (+30%) while the number of mu-, kappa- and total sites was not modified. The affinity at mu-, delta- and kappa-sites was unchanged after 6-OHDA pretreatment.