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Reversal by β‐funaltrexamine of the antinociceptive effect of opioid agonists in the rat
Author(s) -
Hayes Ann G.,
Skingle Malcolm,
Tyers Michael B.
Publication year - 1986
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1986.tb16260.x
Subject(s) - pharmacology , antagonism , opioid , morphine , agonist , tail flick test , chemistry , opioid receptor , fentanyl , antagonist , buprenorphine , receptor , nociception , medicine
1 The effect of the irreversible opioid receptor antagonist, β‐funaltrexamine (β‐FNA), on antin‐ociception produced by μ‐ and κ‐receptor agonists was studied in the rat. 2 β‐FNA, 20 to 80 mg kg −1 , s.c., given 24 h before testing, produced a dose‐related antagonism of the effects of morphine in the paw pressure, hotplate and tail‐flick tests. Following the 80 mg kg −1 dose, the degree of antagonism of morphine was stable for up to 48 h after dosing, but was reduced by 5 days and had disappeared by 8 days. 3 In the paw pressure test, β‐FNA, 40 mg kg −1 , s.c., antagonized the effects of fentanyl, buprenorphine, tifluadom, ethylketocyclazocine and proxorphan; it was without effect against the highly selective κ‐agonist, U‐50,488. 4 In light of these results, the possible opioid receptor selectivities of both the agonists and β‐FNA are reassessed.