Potentiation of transmitter release from NMB human neuroblastoma cells by kappa-opioids is mediated by N-type voltage-dependent calcium channels

The selective kappa-opioid agonist trans-(+/-)-3, 4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl) cyclohexyl] benzenacetamidemethansulfonate (U50,488) potentiates both basal and depolarization-evoked [3H]dopamine release from NMB cells. The potentiation of dopamine release by U50,488 is mediated by N-type voltage-dependent calcium channels since it is blocked by omega-conotoxin, and is resistant to pertussis toxin (PTX)-treatment. When the stimulation of release by U50,488 is blocked by the N-channel antagonist omega-conotoxin, an inhibitory effect on dopamine release is revealed, suggesting that stimulatory and inhibitory effects of U50,488 are exerted in parallel.