GZ coupling to the rat κ‐opioid receptor

Abstract

We have expressed the cloned rat κ‐opioid receptor in human embryonic kidney 293 cells and studied the ability of κ‐selective ligands to inhibit adenylyl cyclase. In transfected 293 cells, activation of the κ‐opioid receptor by U50,488 and the dynorphins resulted in the inhibition of cAMP accumulation. The inhibitory response was sensitive to pertussis toxin and highly selective for κ‐agonists; neither μ‐ nor θ‐opioids were able to activate the κ‐opioid receptor. Upon co‐transfection with the α subunit of G_z, inhibition of cAMP accumulation by κ‐agonist became refractory to pertussis toxin, indicating that the κ‐opioid receptor can couple to both G_i and G_z proteins.