Buprenorphine Blocks - and -Opioid Receptor-Mediated Antinociception in the Mouse

Antagonistic properties of buprenorphine for and -opioid receptors were characterized in -endorphinand [D-Ala,NMe-Phe,Gly-ol]-enkephalin (DAMGO)-induced antinociception, respectively, with the tail-flick test in male ICR mice. -Opioid receptor agonist -endorphin (0.1–1 g), -opioid receptor agonist DAMGO (0.5–20 ng), or buprenorphine (0.1–20 g) administered i.c.v. dose dependently produced antinociception. The antinociception induced by 10 g of buprenorphine given i.c.v. was completely blocked by the pretreatment with -funaltrexamine ( -FNA) (0.3 g i.c.v.), indicating that the buprenophine-induced antinociception is mediated by the stimulation of the -opioid receptor. The antinociceptive effects induced by -endorphin (1 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 g i.c.v.), but not by a higher dose of buprenorphine (10 g i.c.v.). -FNA at a dose (0.3 g i.c.v.) that strongly attenuated DAMGO-induced antinociception had no effect on the antinociception produced by -endorphin (1 g i.c.v.). However, pretreatment with buprenorphine (0.1–10 g) in mice pretreated with this same dose of -FNA was effective in blocking -endorphin-induced antinociception. -FNA was 226-fold more effective at antagonizing the antinociception induced by DAMGO (16 ng i.c.v.) than by -endorphin (1 g i.c.v.). The antinociception induced by -opioid receptor agonist [D-Ala]deltorphin II (10 g i.c.v.) or 1opioid receptor agonist trans-3,4-dichloro-N-methyl-N-(2-[1pyrrolidinyl]cyclohexyl)benzeneacetamine methanesulfonate salt [( )-U50,488H] (75 g i.c.v.) was not affected by pretreatment with buprenorphine (0.1–1.0 g i.c.v.). It is concluded that buprenorphine, at small doses, blocks -opioid receptor-mediated -endorphin-induced antinociception and -opioid receptor-mediated DAMGO-induced antinociception, and at high doses produces a -opioid receptor-mediated antinociception. Buprenorphine, an oripavine derived from thebaine, has widely been shown to be a partial agonist and antagonist of the -opioid receptor, producing both -opioid receptor-mediated antinociception and blocking morphine-induced antinociception in laboratory animals (Cowan et al., 1977; Dum and Herz, 1981; Kamei et al., 1995, 1997). Buprenorphine antagonizes the antinociceptive actions of morphine in the mouse and rat with the tail-flick test, but is not effective in the rat tail-pressure test (Cowan et al., 1977), and also suppresses and precipitates abstinence in morphine-dependent dogs, mice, monkeys and rats (Martin et al., 1976; Cowan et al., 1977; Dum and Herz, 1981). Evidence also supports a -opioid antagonism associated with buprenorphine. Buprenorphine shows potent -opioid antagonist properties in the in vitro [S]GTP S binding assay (Romero et al., 1999). Buprenorphine also blocks the -opioid agonist U-50,488Hinduced inhibition of abdominal stretching induced by intraperitoneal injection of acetic acid in mice (Leander, 1988). However, less data are known for the involvement of buprenorphine to stimulate -opioid receptors or to block -opioid receptors, and some findings are contradicting. The antinociception produced by buprenorphine administered intrathecally is blocked by the -opioid antagonist Win 44,441-3 (Tejwani and Rattan, 2002), whereas buprenorphine given systemically is blocked by pretreatment with selective -opioid receptor antagonist nor-binaltorphimine (Kamei et al., 1995). Neilan et al. (1999) demonstrate that buprenorphine acts as a -opioid antagonist in the [S]GTP S binding assay using C6 glioma cells expressing This work was supported in part by U.S. Public Health Service Grant DA 03811 and DA 12588 from the National Institute on Drug Abuse, National Institutes of Health. Article, publication date, and citation information can be found at http://jpet.aspetjournals.org. DOI: 10.1124/jpet.103.048835. ABBREVIATIONS: GTP S, guanosine 5 -O-(3-thio)triphosphate; DPDPE, [D-Pen,D-Pen]-enkephalin; DAMGO, [D-Ala,N-Me-Phe,Gly-ol]enkephalin; % MPE, percent maximum possible effect; -FNA, -funaltrexamine; DMSO, dimethyl sulfoxide; ANOVA, analysis of variance; ( )-U50, 488H, trans-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]cyclohexyl)benzeneacetamine methanesulfonate salt; Win 44,441-3, 1-cyclopenthyl-5-(1,2,3,4,5,6-hexahydroxy-3,6,11-trimethyl-2-methano-3-benzazocin)-3-pentatone methane sulfonate. 0022-3565/03/3061-394–400$7.00 THE JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS Vol. 306, No. 1 Copyright © 2003 by The American Society for Pharmacology and Experimental Therapeutics 48835/1076304 JPET 306:394–400, 2003 Printed in U.S.A. 394 at A PE T Jornals on Sptem er 3, 2017 jpet.asjournals.org D ow nladed from the cloned -opioid receptor. On the other hand, no differences were found in the dose-response curves in mice treated with either DPDPE alone, or DPDPE and buprenorphine in the hot water tail-flick technique (Pick et al., 1997). Buprenorphine is also identified to exhibit -opioid receptor binding activity using the nonselective ligand ( )[H]ethylketocyclazocine, in the presence of selective -, -, and 1-opioid receptor agonists (Nock et al., 1990, 1993; Nock, 1995). Unlike -endorphin, whose affinity to the -opioid receptor is decreased by high concentration of NaCl, the affinities of buprenorphine to the -opioid receptor are increased by high concentration of NaCl, suggesting that buprenorpine might be an antagonist for the -opioid receptor (Nock et al., 1990). Buprenorphine blocks the increase of [S]GTP S binding induced by -agonist -endorphin in the pons/medulla membrane obtained from -opioid receptor knockout mice (Mizoguchi et al., 2002). This finding indicates that buprenorphine acts as an -opioid receptor antagonist to block the -endorphin-induced G protein activation in the pons/medulla membrane of mice that genetically lack -opioid receptors. The present study was designed to further characterize the antagonistic properties of buprenorphine for and -opioid receptor-mediated antinociception induced by -opioid receptor agonist -endorphin and -opioid receptor agonist [D-Ala,N-Me-Phe,Gly-ol]-enkephalin (DAMGO), in mice. We report here for the first time that buprenorphine blocks and -opioid receptor-mediated antinociception induced by i.c.v.-administered -endorphin and DAMGO, respectively. In addition, antinociceptive property induced by high doses of buprenorphine, which is mediated by the stimulation of -opioid receptors, was also characterized. Materials and Methods Animals. Male ICR mice, weighing 23 to 25 g (Charles River Laboratories, Inc., Wilmington, MA), were used. Animals were housed five per cage in a room maintained at 22 0.5°C with an alternating 12-h light/dark cycle. Food and water were available ad libitum. Animals were used only once. All experiments were approved by and conformed to the guidelines of the Medical College of Wisconsin Animal Care Committee. Every effort was made to minimize the number and any suffering of animals used in the following