Role of MT1 melatonin receptors in methamphetamine-induced locomotor sensitization in C57BL/6 mice.
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ABSTRACT: Melatonin modifies physiological and behavioral responses to psychostimulants, with the MT? and MT? melatonin receptors specifically implicated in facilitating methamphetamine (METH)-induced sensitization in melatonin-proficient mice.The objective of the study is to assess differences in locomotor sensitization after a single dose of methamphetamine in low-melatonin-expressing C57BL/6 wild-type and MT? receptor knockout (MT?KO) mice, comparing with melatonin-expressing C3H/HeN mice.Mice received a vehicle or methamphetamine (1.2 mg/kg, i.p.) pretreatment (day 1) during the light (ZT5-9) or dark (ZT 19-21) periods in novel test arenas. Locomotor sensitization was assessed by methamphetamine challenge after an eight-day abstinence (day 9). TH protein expression was evaluated by immunofluorescence and Western blot analysis.Methamphetamine pretreatment induced statistically significant locomotor sensitization upon challenge after eight-day abstinence in C3H and C57 wild-type mice during the light period. The magnitude of sensitization in C57 mice was diminished in the dark period and completely abrogated in MT?KO mice. No differences were observed in tyrosine hydroxylase immunoreactivity in the mesolimbic dopamine system. Additional exposures to the test arenas after methamphetamine pretreatment (nights 2-6) enhanced sensitization.Deletion of the MT? melatonin receptor abolishes sensitization induced by a single METH pretreatment. The magnitude of sensitization is also altered by time of day and contextual cues. We conclude that the MT? melatonin receptor is emerging as a novel target of therapeutic intervention for drug abuse disorders.
SUBMITTER: Hutchinson AJ
PROVIDER: S-EPMC4696604 | biostudies-literature | 2014 Jan
REPOSITORIES: biostudies-literature
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