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J Pharmacol Exp Ther. 2003 Jul;306(1):394-400. Epub 2003 Apr 29.

Buprenorphine blocks epsilon- and micro-opioid receptor-mediated antinociception in the mouse.

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  • 1Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA.

Abstract

Antagonistic properties of buprenorphine for epsilon- and micro -opioid receptors were characterized in beta-endorphin- and [d-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO)-induced antinociception, respectively, with the tail-flick test in male ICR mice. epsilon-Opioid receptor agonist beta-endorphin (0.1-1 micro g), micro -opioid receptor agonist DAMGO (0.5-20 ng), or buprenorphine (0.1-20 micro g) administered i.c.v. dose dependently produced antinociception. The antinociception induced by 10 micro g of buprenorphine given i.c.v. was completely blocked by the pretreatment with beta-funaltrexamine (beta-FNA) (0.3 micro g i.c.v.), indicating that the buprenophine-induced antinociception is mediated by the stimulation of the micro -opioid receptor. The antinociceptive effects induced by beta-endorphin (1 micro g i.c.v.) and DAMGO (16 ng i.c.v.) were dose dependently blocked by pretreatment with smaller doses of buprenorphine (0.001-1 micro g i.c.v.), but not by a higher dose of buprenorphine (10 micro g i.c.v.). beta-FNA at a dose (0.3 micro g i.c.v.) that strongly attenuated DAMGO-induced antinociception had no effect on the antinociception produced by beta-endorphin (1 micro g i.c.v.). However, pretreatment with buprenorphine (0.1-10 micro g) in mice pretreated with this same dose of beta-FNA was effective in blocking beta-endorphin-induced antinociception. beta-FNA was 226-fold more effective at antagonizing the antinociception induced by DAMGO (16 ng i.c.v.) than by beta-endorphin (1 micro g i.c.v.). The antinociception induced by delta-opioid receptor agonist [d-Ala2]deltorphin II (10 micro g i.c.v.) or kappa1-opioid receptor agonist trans-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]cyclohexyl)benzeneacetamine methanesulfonate salt [(-)-U50,488H] (75 micro g i.c.v.) was not affected by pretreatment with buprenorphine (0.1-1.0 micro g i.c.v.). It is concluded that buprenorphine, at small doses, blocks epsilon-opioid receptor-mediated beta-endorphin-induced antinociception and micro -opioid receptor-mediated DAMGO-induced antinociception, and at high doses produces a micro -opioid receptor-mediated antinociception.

PMID:
12721333
[PubMed - indexed for MEDLINE]
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