Identification of arodyn, a novel acetylated dynorphin A-(1-11) analogue, as a kappa opioid receptor antagonist.

Arodyn (aromatic dynorphin) is a novel analogue of the opioid peptide dynorphin A with a nonbasic N-terminus that exhibits nanomolar affinity (K(i) = 10 nM) and remarkable selectivity for kappa opioid receptors (K(i) ratio (kappa/mu/delta) = 1/174/583). Arodyn completely reverses the agonism of dynorphin A (1-13)NH(2) in a concentration-dependent manner in the adenylyl cyclase assay. Thus arodyn is a novel kappa opioid receptor selective antagonist that will be useful to study these receptors.