Authors: Thierry Le Marec Cynthia MarieClaire Florence Noble Nicolas Marie
Publish Date: 2011/02/22
Volume: 216, Issue: 2, Pages: 297-303
Abstract
We compared the effects of intermittent 20 mg/kg once daily for 7 days and chronic escalating doses from 5 to 40 mg/kg three times a day for 5 days morphine treatments in mice on locomotor activity We also quantified by autoradiography mu opioid receptor MOR in ventral tegmental area VTA dopamine D1 D1R and D2 D2R receptors in striatumWhereas the intermittent treatment led to a longterm sensitization to locomotor effects of morphine until withdrawal day WD 14 the chronic treatment induced a tolerance WD1 followed by a transient sensitization WD14 Binding studies demonstrated a decrease of MOR in VTA at WD1 for the chronic treatment In contrast striatal D1R level was decreased at WD1 and increased at WD14 for the chronic treatment For the D2R we observed a decrease from WD1 to WD14 for the intermittent treatment and an increase at WD1 followed by a decrease at WD14 for the chronic treatmentThierry Le Marec was a recipient of a fellowship from the Fondation pour la Recherche Médicale The authors wish to thank Dr Ana Cardona Unité de Recherche et dExpertise Histotechnologie et Pathologie Institut Pasteur Paris for her help on Beta imager and helpful comments on the manuscript The authors would also like to thank the quantitative realtime PCR and animal care facilities of the Institut MédicamentToxicologieChimie Environnement IMTCE Université Paris Descartes Paris France
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