Tolerance to effects of morphine without cross tolerance to effects of clonidine on schedule-controlled behavior of pigeons |
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| Authors: | Jonathan L. Katz |
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| Affiliation: | (1) Preclinical Pharmacology Branch, NIDA Addiction Research Center and Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, P.O. Box 5180, 21224 Baltimore, MD, USA |
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| Abstract: | Schedule-controlled responding was maintained under a multiple fixed-interval, fixed-ratio schedule in pigeons. Dose-related decreases in response rates were produced by clonidine (0.001–0.1 mg/kg) and morphine (0.3–5.6 mg/kg). Chronic administration of morphine produced (1) tolerance to effects of morphine, as evidenced by a decrease in potency of morphine and (2) sensitivity to opioid antagonists, as evidenced by an increase in potency of naloxone. Dose-effect curves for clonidine were not appreciably altered by chronic morphine administration.Offprint requests to: J.L. Katz |
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| Keywords: | Clonidine Morphine Naloxone Schedule-controlled responding Chronic administration Tolerance Cross tolerance Pigeons |
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