title: Locomotor activity: A distinctive index in morphine self-administration in rats.
abstract: Self-administration of addictive drugs is a widely used tool for studying behavioral, neurobiological, and genetic factors in addiction. However, how locomotor activity is affected during self-administration of addictive drugs has not been extensively studied. In our present study, we tested the locomotor activity levels during acquisition, extinction and reinstatement of morphine self-administration in rats. We found that compared with saline self-administration (SA), rats that trained with morphine SA had higher locomotor activity. Rats that successfully acquired SA also showed higher locomotor activity than rats that failed in acquiring SA. Moreover, locomotor activity was correlated with the number of drug infusions but not with the number of inactive pokes. We also tested the locomotor activity in the extinction and the morphine-primed reinstatement session. Interestingly, we found that in the first extinction session, although the number of active pokes did not change, the locomotor activity was significantly lower than in the last acquisition session, and this decrease can be maintained for at least six days. Finally, morphine priming enhanced the locomotor activity during the reinstatement test, regardless of if the active pokes were significantly increased or not. Our results clearly suggest that locomotor activity, which may reflect the pharmacological effects of morphine, is different from drug seeking behavior and is a distinctive index in drug self-administration.
authors.affiliation: CAS Key Laboratory of Mental Health, Institute of Psychology, Beijing, China.|Department of Psychology, University of Chinese Academy of Sciences, Beijing, China.|Laboratory of Neurobiology and the National Laboratory of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing, China.
authors.forename: Jian-Jun
authors.identifier: http://orcid.org/0000-0001-7526-7234
authors.initials: JJ
authors.lastname: Zhang
authors.affiliation: Laboratory of Neurobiology and the National Laboratory of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing, China.
authors.forename: Qingyao
authors.initials: Q
authors.lastname: Kong
mesh_terms: D000818:Animals; D058999:Drug-Seeking Behavior / Q000502:physiology; D005108:Extinction, Psychological / Q000502:physiology; D008124:Locomotion / Q000187:drug effects* / Q000502:physiology; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012054:Reinforcement, Psychology; D012646:Self Administration / Q000379:methods
chemical_list: D009020:Morphine