The role of opiate receptors in the potentiation of pentobarbital sleeping time by the acute and chronic administration of opiates |
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Authors: | R N Pechnick G W Terman |
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Institution: | Department of Pharmacology, School of Medicine, U.C.L.A. 90024. |
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Abstract: | Male rats injected with pentobarbital (50.0 mg/kg i.p.) showed increased sleeping time after the acute administration of morphine (5.0 or 10.0 mg/kg s.c.). This effect was antagonized by naltrexone (2.0 mg/kg s.c.). The enhancement displayed stereoselectivity as levorphanol greatly lengthened the sleeping time induced by pentobarbital while dextrophan only produced a slight increase. Rats implanted for 3 days with pellets of morphine base (75.0 mg) were tolerant to the analgesic effects of morphine (2.5 mg/kg s.c.) but showed an even greater increase in pentobarbital-induced sleeping time than rats treated acutely. No potentiation was observed in subjects that were also implanted with a pellet of naltrexone (30.0 mg). It is concluded that the potentiation of pentobarbital-induced sleeping time produced by opiates is mediated by opiate receptors, but fails to show the development of tolerance. |
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