Buprenorphine and gastrointestinal transit in rats: effect of naloxone on the biphasic dose-response curve.
1. Buprenorphine (0.01-10 mg/kg, subcutaneous [s.c.]) slowed the passage of a charcoal meal along the gastrointestinal tract in rats. The dose-response relationship was U-shaped. 2. When rats were pretreated with naloxone (0.30 mg/kg, s.c.), both the descending and ascending components of the buprenorphine dose-response curve were displaced to the right. 3. Buprenorphine-induced delay of transit was maximal at a dose of 0.10 mg/kg. In rats pretreated with naloxone, a 30-fold higher dose of buprenorphine was required for a comparable peak effect. 4. Moderate-high doses of buprenorphine may be acting on a functionally related binding site which non-competitively inhibits the usual buprenorphine-mu opioid receptor interaction.
Cowan
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Department of Pharmacology, Reckitt & Colman, Hull, UK.
D000279:Administration, Cutaneous; D000818:Animals; D002047:Buprenorphine / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005772:Gastrointestinal Transit / Q000187:drug effects*; D008297:Male; D009270:Naloxone / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D009270:Naloxone; D002047:Buprenorphine