kappa-opioid agonist stimulated regional distribution of [(35)S]GTPgammas binding in butorphanol continuously infused rat.
Butorphanol is a mixed agonist/antagonist opioid analgesic agent, which exerts its effects mainly by interaction with the kappa-opioid receptor. Opioid receptors are coupled to G proteins of G(i)/G(o) family, and recently a decrease in micro-opioid activation of G proteins has been reported in specific brainstem nuclei after chronic morphine administration. The influence of centrally administered butorphanol on agonist-stimulated G protein coupling was examined in the rat brain, using in situ guanylyl-5'-O-(gamma-[(35)S]thio)-triphosphate (GTPgammaS) binding autoradiography. Rats were treated with butorphanol (26 nmol/microl/h) by intracerebroventricular infusion via osmotic minipumps for 3 days. The distribution of [(35)S]GTPgammaS binding in the brain 7 h after the termination of butorphanol infusion was measured in the presence or absence of the selective kappa-opioid agonist, U-50,488. This agonist significantly increased [(35)S]GTPgammaS binding in the parietal cortex, caudate putamen, thalamus, and central gray of control rats, but not in those regions of the butorphanol-infused animals. These results suggest that chronic administration of butorphanol developed tolerance and abolished U-50,488 activation of G proteins in these brain areas.
Park
Y
Y
Department of Pharmacology, College of Pharmacy, Seoul National University, Kwanak-Gu, Seoul, South Korea.
Jang
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CG
Ho
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Ko
K H
KH
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000494:pharmacology*; D000818:Animals; D002077:Butorphanol / Q000494:pharmacology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism*; D007260:Infusion Pumps; D007276:Injections, Intraventricular; D008297:Male; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017473:Receptors, Opioid, kappa / Q000819:agonists*; D013462:Sulfur Radioisotopes; D014018:Tissue Distribution / Q000187:drug effects
D009292:Narcotic Antagonists; D009294:Narcotics; D017473:Receptors, Opioid, kappa; D013462:Sulfur Radioisotopes; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D002077:Butorphanol