Please cite this article in press as: Mokhtarizaer A, et al. Effects of voluntary and treadmill exercise on spontaneous withdrawal signs, cognitive deficits and alterations in apoptosis-associated proteins in morphine-dependent rats. Behav Brain Res (2014), http://dx.doi.org/10.1016/j.bbr.2014.05.061 ARTICLE IN PRESS G Model BBR 8952 1–11 Behavioural Brain Research xxx (2014) xxx–xxx Contents lists available at ScienceDirect Behavioural Brain Research jou rn al hom epage: www.elsevier.com/locate/bbr Research report Effects of voluntary and treadmill exercise on spontaneous withdrawal signs, cognitive deficits and alterations in apoptosis-associated proteins in morphine-dependent rats Amin Mokhtarizaer a , Shahrbanoo Ghodrati-Jaldbakhan a , Abbas Ali Vafaei a , Q1 Houssien Milad-Gorji a , Maziar M. Akhavan b , Ahmaed Reza Bandehgi a,b , Ali Rashidy-Pour a,∗ a Laboratory of Learning and Memory, Research Center and Department of Physiology, School of Medicine, Semnan University of Medical Sciences, Semnan, Q2 Iran b Skin Research Center, Laboratory of Protein and Enzyme, ShahidBeheshti University (M.C.), Shohada-e Tajrish Hospital, Shahrdari St., 1989934148 Tehran, Iran h i g h l i g h t s • Chronic morphine leads to apoptosis and impairment of cognitive functions. • Voluntary and treadmill exercise enhances cognitive functions. • Exercise suppress chronic morphine-induced apoptosis. • Exercise alleviates memory impairment induced by chronic morphine. • Exercise could be a potential method to ameliorate the adverse effects of opiate abuse. a r t i c l e i n f o Article history: Received 30 March 2014 Received in revised form 23 May 2014 Accepted 27 May 2014 Available online xxx Keywords: Treadmill exercise Voluntary exercise Chronic morphine Cognitive defect Apoptosis a b s t r a c t Chronic exposure to morphine results in cognitive deficits and alterations of apoptotic proteins in favor of cell death in the hippocampus, a brain region critically involved in learning and memory. Physical activity has been shown to have beneficial effects on brain health. In the current work, we examined the effects of voluntary and treadmill exercise on spontaneous withdrawal signs, the associated cognitive defects, and changes of apoptotic proteins in morphine-dependent rats. Morphine dependence was induced through bi-daily administrations of morphine (10 mg/kg) for 10 days. Then, the rats were trained under two different exercise protocols: mild treadmill exercise or voluntary wheel exercise for 10 days. After exercise training, their spatial learning and memory and aversive memory were examined by a water maze and by an inhibitory avoidance task, respectively. The expression of the pro-apoptotic protein Bax and the anti- apoptotic protein Bcl-2 in the hippocampus were determined by immunoblotting. We found that chronic exposure to morphine impaired spatial and aversive memory and remarkably suppressed the expression of Bcl-2, but Bax expression remained constant. Both voluntary and treadmill exercise alleviated memory impairment, increased the expression of Bcl-2 protein, and only the later suppressed the expression of Bax protein in morphine-dependent animals. Moreover, both exercise protocols diminished the occurrence of spontaneous morphine withdrawal signs. Our findings showed that exercise reduces the spontaneous morphine-withdrawal signs, blocks the associated impairment of cognitive performance, and overcomes morphine-induced alterations in apoptotic proteins in favor of cell death. Thus, exercise may be a useful therapeutic strategy for cognitive and behavioral deficits in addict individuals. © 2014 Published by Elsevier B.V. ∗ Corresponding author at: Research Center and Department of Physiology, Sem- Q3 nan University of Medical Sciences, 15131-38111 Semnan, Iran. Tel.: +98 09121140221; fax: +98 2313354186. E-mail address: Rashidy-pour@semums.ac.ir (A. Rashidy-Pour). 1. Introduction Chronic exposure to opiates can induce cognitive deficits in humans, and experimental animals [1–8], and also leads to changes in spine density, neurogenesis and synaptic transmission in the hip- pocampus of rats [9,10]. Prenatal morphine exposure also impairs http://dx.doi.org/10.1016/j.bbr.2014.05.061 0166-4328/© 2014 Published by Elsevier B.V. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40