Stereospecific dextrorphan tolerance in rats.
1 Levorphanol was 20 times more potent than dextrorphan in decreasing food-reinforced fixed ratio 15 responding in male Sprague Dawley rats. 2 Chronic dextrorphan (100 mg/kg, i.p.; every 8 h) resulted in the development of dextrorphan tolerance. The dextrorphan dose-effect curve was shifted to the right three fold. 3 In contrast to dextrorphan, nontolerance developed to the effects of levorphanol. 4 These data support the hypothesis that (+)-isomers of opioids produce pharmacologically distinct CNS effects.
D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects*; D003864:Depression, Chemical; D003917:Dextrorphan / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance; D005502:Food; D007981:Levorphanol / Q000494:pharmacology*; D008297:Male; D009019:Morphinans / Q000494:pharmacology*; D051381:Rats
D009019:Morphinans; D003917:Dextrorphan; D007981:Levorphanol