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Updated: Aug 10, 2026

Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
Published on: July 29, 2014
The production of morphine tolerance and physical dependence by the oral route in the rat. A comparative study
Abstract:
A method for the chronical administration of morphine by the oral route is discussed and compared with the production of physical dependence to morphine by injection. The method recommends the administration of Morphine HCl dissolved in a 45% sucrose syrup and given orally for 4 weeks. The initial concentration of morphine in the syrup was 1 mg/ml and was increased weekly up to 4 mg/ml at the end of the experiment. This procedure rendered the animals physically dependent on morphine as observed by drug withdrawal, when abstinence symptoms were easily identified.
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