Differential effects of systemically administered nor-binaltorphimine (nor-BNI) on κ-opioid agonists in the mouse writhing assay (original) (raw)

Abstract

The opioid antagonist effects of systemically administered nor-binaltorphimine (nor-BNI) were evaluated against the kappa agonists CI-977, U69,593, U50,488, ethylketocyclazocine (EKC), Mr2034 and bremazocine, the mu agonist morphine and the alkaloid delta agonist BW-373U86 in the acetic acid-induced writhing assay in mice. All eight agonists completely and dose-dependently inhibited writhing. Antagonism of CI-977 was apparent 1 h after administration of 32 mg/kg nor-BNI, peaking after 4 h and was maintained for at least 4 weeks; no antagonist effects of nor-BNI were apparent after 8 weeks. Nor-BNI (32 mg/kg) caused little or no antagonism of morphine or BW-373U86 at 1 h and none at 24 h after nor-BNI administration. Subsequently, dose-effect curves for CI-977, U50,488, U69,593, EKC, Mr2034 and bremazocine were determined 24 h after pretreatment with 3.2, 10 and 32 mg/kg nor-BNI. Pretreatment with 3.2 mg/kg nor-BNI produced significant antagonism of all six kappa agonists, suggesting that their antinociceptive effects were mediated at least in part by nor-BNI-sensitive kappa receptors. At higher doses, nor-BNI dose-depend-ently shifted the agonist dose-effect curves of CI-977, U50,488, U69,593 and bremazocine, but not those of EKC and Mr2034, suggesting that the latter compounds may be producing effects via nor-BNI-insensitive receptors. Mu receptor involvement was demonstrated following a 24 h pretreatment with 32 mg/kg_β_-FNA in combination with nor-BNI, which significantly increased the degree of antagonism of Mr2034 and EKC from that seen with nor-BNI alone. Hence, SC administered nor-BNI selectively antagonized agonist activity mediated through kappaopioid receptors without differentiating between kappa subtypes. Nor-BNI also enabled the mu agonist activity of proposed kappa agonists to be measured.

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Authors and Affiliations

  1. Department of Pharmacology, University of Michigan, 48109, Ann Arbor, MI, USA
    Jillian H. Broadbear, S. Stevens Negus, Eduardo R. Butelman & James H. Woods
  2. Department of Psychology, University of Michigan, 48109, Ann Arbor, MI, USA
    James H. Woods
  3. NIH-NIDDK, 20892, Bethesda, MD, USA
    Brian R. de Costa

Authors

  1. Jillian H. Broadbear
  2. S. Stevens Negus
  3. Eduardo R. Butelman
  4. Brian R. de Costa
  5. James H. Woods

Additional information

A preliminary report of these findings was made at the International Narcotic/Research/Conference in Keystone, CO, June, 1992. This work was supported by USPHS grant DA 00254. Animals used in these studies were maintained in accordance with the University Committee on Use and Care of Animals, University of Michigan, and guidelines of the Committee on Care and Use of Laboratory Animal Resources, National Research Council (Department of Health, Education and Welfare, Publication No. (NIH) 85-23, revised 1983)

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Broadbear, J.H., Stevens Negus, S., Butelman, E.R. et al. Differential effects of systemically administered nor-binaltorphimine (nor-BNI) on κ-opioid agonists in the mouse writhing assay.Psychopharmacology 115, 311–319 (1994). https://doi.org/10.1007/BF02245071

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