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A single exposure to morphine induces long‐lasting sensitization: age‐related differences in mice
Author(s) -
Koek Wouter
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.886.6
Subject(s) - sensitization , morphine , context (archaeology) , medicine , young adult , saline , dose–response relationship , anesthesia , pharmacology , endocrinology , immunology , biology , paleontology
Given evidence for age‐related differences in effects of drugs of abuse, surprisingly few studies have explored effects of opioids in adolescents (versus adults). This study compared locomotor sensitization in adolescent and adult mice after a single exposure to morphine. Adolescent (postnatal day 29) and adult male C57BL/6J mice were treated with saline or morphine (1–100 mg/kg, i.p.) (session 1), and morphine (10 mg/kg)‐induced locomotion was assessed 3–36 days later (session 2). Morphine during session 1 dose‐dependently enhanced the locomotor‐stimulating effects of 10 mg/kg morphine during session 2. The minimum significant dose was 3.2 mg/kg in adults and 32 mg/kg in adolescents, and the maximal enhancement was 200% in adults and 150% in adolescents. Irrespective of age, the enhancement increased with the length of the intersession interval, attained a maximum at 1 week, and remained unchanged at 2 and 5 weeks. In adults, but not in adolescents, the enhancement was largest when both sessions were conducted in the same environment. These results show that a single exposure to morphine induces dose‐, delay‐, and context dependent sensitization in adults. In adolescents, morphine induces sensitization less potently, less efficaciously, and less dependent on the context than in adults, but its sensitizing effects are as long‐lasting as in adults, and last into adulthood. Supported by DA23261