Characterization of kappa-3 opioid receptors

Evidence suggesting opioid receptor subtypes is based on more than twenty years of opioid receptor research, and these subtypes should prove important in the development of new therapeutic agents with novel pharmacological profiles and minimal side effects. Three major families of the receptors have been proposed: mu, delta and kappa. This thesis explores a novel opioid receptor subtype, kappa{dollar}sb3,{dollar} originally based upon studies with naloxone benzoyl-hydrazone.; In the present research, we demonstrated kappa{dollar}sb3{dollar} receptors in mouse brain tissue and correlated them to their pharmacology. In addition to a density of approximately twice that for mu receptors in mice whole brain, kappa{dollar}sb3{dollar} receptors differ from traditional mu, delta, kappa receptors in their binding selectivity profiles. Proceeding to cell culture experiments, we examined the signal transduction of kappa{dollar}sb3{dollar} receptors. BE(2)-C and SH-SY5Y cells contain high levels of mu and kappa{dollar}sb3{dollar} receptors and lower levels of delta receptors. All subtypes inhibit adenylate cyclase in a pertussis toxin-sensitive manner. However, their actions could be readily distinguished from each other by antagonists and other treatments. Finally we cloned a kappa{dollar}sb3{dollar}-related receptor from mouse brain. This receptor has high homology with the mu, delta and kappa opioid receptors. Antisense studies with an oligodeoxynucleotide directed against a region of the third extracellular loop revealed a selective blockade of kappa{dollar}sb3{dollar} analgesia. Mu, delta and kappa{dollar}sb1{dollar} opioid analgesia was unaffected by this antisense treatment. These results further support the hypothesis of a novel kappa{dollar}sb3{dollar} opioid receptor that is distinct from the mu, delta and kappa{dollar}sb1{dollar} opioid receptors.