USE OF BETA-FUNALTREXAMINE TO DETERMINE MU-OPIOID RECEPTOR INVOLVEMENT IN THE ANALGESIC ACTIVITY OF VARIOUS OPIOID LIGANDS

  • 1 May 1987
    • journal article
    • research article
    • Vol. 241  (2) , 374-378
Abstract
Systemic administration of .beta.-funaltrexamine (.beta.-FNA) 24 hr before analgesic testing produced approximately a 10-fold parallel shift in the dose-response curves of the prototypic mu agonists morphine, I-methadone, fentanyl and etorphine in the mouse abdominal constriction test. In contrast, prior administration of .beta.-FNA produced no appreciable shift in the analgesic dose-response curve of the selective kappa agonist, U-50, 488H. These results suggest that .beta.-FNA is selective for mu over kappa receptors under the conditions used in this study. The dose-response curves for ethylketazocine and proxorphan were affected only to a small extent by .beta.-FNA pretreatment, suggesting that these compounds have analgesic actions mediated primarily through nonmu, probably kappa receptors. The dose-response curves for cyclazocine, buprenorphine, butorphanol, nalorphine and nalbuphine were shifted markedly to the right and frequently not in a parallel fashion by the prior adminstration of .beta.-FNA. These results seem to indicate a major role for the mu receptor in the analgesic actions of these compounds.