title: Pharmacological characterization of the epsilon-opiate receptor.
abstract: The epsilon-opiate receptor of the electrically stimulated rat vas deferens has been characterized by means of beta-endorphin, its fragments and derivatives thereof, as well as by its tolerance development. The data provide evidence for the uniqueness of the epsilon-receptor as compared to mu- and delta-receptors of the guinea-pig ileum and the mouse vas deferens, respectively. It appears that an activation of the epsilon-receptor requires at least the beta-endorphin sequence 1-21, which sharply contrasts with the relatively high sensitivity of mu- and delta-receptors to much shorter fragments of this opioid peptide. Furthermore, after chronic exposure of rats to etorphine, the isolated vas deferens shows a dramatic loss of sensitivity to mu-receptor agonists, but only a moderate decrease in sensitivity to beta-endorphin. The presented data contribute to the characterization of a distinct novel type of opiate receptor, the epsilon-receptor.
mesh_terms: D000818:Animals; D004723:Endorphins / Q000494:pharmacology*; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D051381:Rats; D011957:Receptors, Opioid / Q000187:drug effects*; D014649:Vas Deferens / Q000187:drug effects
chemical_list: D004723:Endorphins; D011957:Receptors, Opioid