COMPARATIVE-STUDY OF THE EFFECTS OF MU-OPIOID, DELTA-OPIOID AND KAPPA-OPIOID AGONISTS ON 3H-DOPAMINE UPTAKE IN RAT STRIATUM AND NUCLEUS-ACCUMBENS

The effect of the mu opioid agonist DAGO, delta opioid agonist DPDPE and kappa opioid agonist U50,488H on 3H-dopamine (3H-DA) uptake was studied in synaptosomes prepared from rat striatum and nucleus accumbens. Over the range of concentrations tested (1 nM-10 mu M) DAGO and DPDPE were devoid of effects on 3H-DA uptake in the striatum and the nucleus accumbens. In contrast, U50,488H significantly decreased 3H-DA uptake in both structures. The inhibition of uptake induced by the kappa agonist was not reversed in the presence of the opiate antagonists naloxone (10 mu M) or nor-binaltorphimine (0.1 mu M). Dynorphin A (1-13) also induced a significant reduction in 3H-DA uptake in both structures at the concentrations of 10 and 30 mu M. This inhibitory effect was not reversed by naloxone (10 mu M). These data suggest that kappa opioid agonists modulate dopamine uptake in the striatum and the nucleus accumbens and their effects may not be due to an activation of opioid receptors.