title: The sensitivity of opioid receptor types to regulation by sodium and GTP.
abstract: The effects of Na+ and GTP on agonist binding to mu, delta, and kappa opioid binding sites in membranes from guinea pig cortex have been studied. All incubations were in a modified Krebs-Hepes buffer at 37 degrees; effects of Na+ were evaluated by replacement with an equal concentration of K+. mu binding sites appeared more sensitive than delta sites, while kappa sites were the least sensitive to both regulators. However, even at kappa sites, Na+ induced a significant reduction in agonist affinity and GTP caused a significant reduction in maximum binding.
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D011957:Receptors, Opioid / Q000187:drug effects*; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D012964:Sodium / Q000494:pharmacology*
chemical_list: D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D006160:Guanosine Triphosphate; D012964:Sodium