Effects of opioids in morphine-treated pigeons trained to discriminate among morphine, the low-efficacy agonist nalbuphine, and saline. The Journal of pharmacology and experimental therapeutics. [J Pharmacol Exp Ther] Journal article | | Title | Effects of opioids in morphine-treated pigeons trained to discriminate among morphine, the low-efficacy agonist nalbuphine, and saline. | | Author(s) | Walker EA, Picker MJ, Granger A, Dykstra LA | | Institution | Department of Psychology, University of North Carolina at Chapel Hill, USA. ellen.walker@temple.edu | | Source | J Pharmacol Exp Ther 2004 Jul; 310(1):150-8. | | MeSH | Animals
Columbidae
Conditioning, Operant
Discrimination Learning
Disease Models, Animal
Morphine
Morphine Dependence
Nalbuphine
Narcotics
Research Support, U.S. Gov't, P.H.S.
Sodium Chloride
| | Abstract | In opioid-dependent subjects, the low-efficacy mu agonist nalbuphine generally precipitates withdrawal or withdrawal-like stimulus effects. To provide a more complete characterization of the discriminative stimulus effects of nalbuphine in opioid-treated subjects, seven White Carneux pigeons were treated daily with 10 mg/kg morphine i.m. and trained 6 h later to discriminate among 10 mg/kg morphine, 1.0 mg/kg nalbuphine, and saline by responding on one of three different keys. When tested, morphine produced morphine-key responding and nalbuphine produced nalbuphine-key responding. Replacing the daily morphine injection with saline produced nalbuphine-key responding, and this effect was reversed by the administration of morphine. In substitution tests with other compounds, the antagonists naltrexone (i.m.) and CTAP (D-Phe-Cys-Tyr-D-Tryp-Lys-Thr-Pen-Thr-NH2) (i.c.v.) produced nalbuphine-key responding. High-efficacy agonists fentanyl and etorphine produced morphine-key responding. The intermediate-efficacy agonists buprenorphine, dezocine, and butorphanol produced a pattern of morphine-, saline-, and/or nalbuphine-key responding that differed across individual pigeons. The lower efficacy agonists nalorphine and levallorphan produced predominantly nalbuphine-key responding. The kappa agonists spiradoline and U50,488 [trans-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]cyclohexyl)benzeneacetamide methanesulfonate], the nonopioid d-amphetamine, and saline produced predominantly saline-key responding. Naltrexone and nalbuphine dose dependently reversed the morphine-key responding produced by the training dose of morphine. Together, these data suggest that the discriminative-stimulus effects of the low-efficacy micro agonist nalbuphine in morphine-treated pigeons are similar to those of other low-efficacy agonists, naltrexone, and the termination of daily morphine treatment. | | Language | eng | | Pub Type(s) | Journal Article
| | PubMed ID | 15044559 |
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