mortality/aging
• at 750 mg/kg morphine, 25% of homozygotes lived while all wild-type littermates died
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behavior/neurological
• null mice unlike wild-type show no preference for environments paired with 10 mg/kg morphine
• nulls displayed lower lever-pressing behavior at a dose of 1 mg/kg/injection of morphine than heterozygotes or wild-type
• in naloxone-precipitated withdrawal after 5 days of chronic morphine administration, homozygotes show no withdrawal-related jumping but heterozygotes and wild-type did after pretreatment for 3 days
• null mice show no increase in locomotor activity in response to morphine
• in homozygotes, administration of morphine does not induce analgesia (no increase in latency to respond) in tail flick or hot plate tests
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• in homozygotes, administration of morphine does not induce analgesia (no increase in latency to respond) in tail flick or hot plate tests
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• homozygotes display shorter latencies in the tail flick test compared to wild-type at water temperatures of 50 and 53 degrees
• at 55 degrees, there is a decrease in time to first paw lick in mutants
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homeostasis/metabolism
• at 750 mg/kg morphine, 25% of homozygotes lived while all wild-type littermates died
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