Given evidence for age-related differences in the effects of drugs of abuse, surprisingly few preclinical studies have explored effects of opioids in adolescents (versus adults).

This study compared the motor stimulating and ataxic effects of repeatedly administered morphine in in adolescent, late adolescent, and adult mice.

Mice were treated with saline or morphine (10-100 mg/kg, i.p.) once per day for 4 days, and morphine (3.2-56 mg/kg)-induced locomotion was assessed 3 days or 5 weeks later. Different mice were treated repeatedly with morphine and ataxia was measured.

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