Binding characteristics of kappa opioids in rat brain. A comparison of in vitro binding paradigms.
Putative kappa binding was investigated in homogenates of the brain of the rat using [3H]ethylketocylazocine and [3H]diprenorphine under conditions where mu and delta sites were blocked. Under blocked conditions, the binding of [3H]ethylketocyclazocine labelled a single site, as defined by kinetic and equilibrium analysis, which showed high affinity for dynorphin 1-17, U50,488H, and benzomorphan compounds. However, blocked binding of [3H]diprenorphine showed a biphasic dissociation curve, and did not show high affinity for the specific kappa agonists dynorphin 1-17 or U50,488H. It is proposed that blocked [3H]ethylketocyclazocine is the more appropriate paradigm to study putative kappa binding, while blocked [3H]diprenorphine may label additional non-mu/non-delta sites.
Weyhenmeyer
J A
JA
Mack
K J
KJ
D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D003496:Cyclazocine / Q000031:analogs & derivatives* / Q000378:metabolism; D004174:Diprenorphine / Q000378:metabolism*; D016314:Ethylketocyclazocine; D007700:Kinetics; D008297:Male; D009019:Morphinans / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000378:metabolism*; D017473:Receptors, Opioid, kappa
D009019:Morphinans; D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa; D004174:Diprenorphine; D016314:Ethylketocyclazocine; D003496:Cyclazocine