Journal of Research in Medical Sciences1735-199591200402012633Department of Pharmacology, School of Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, IranDepartment of Pharmacology, School of Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, IranDepartment of Pharmacology, School of Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran20070217Background: There is growing evidence indicating that neuronal calcium channels play an important role in the mechanism of Morphine dependence. Objective: To investigate the acute and long-term effects of Verapamil in Morphine dependent mice. Methods: Mice were rendered dependent on Morphine by subcutaneous injection of Morphine over a period of 5 days. The effects of acute and chronic administration of phenylalkylamine calcium channel antagonist, Verapamil, on Naloxone induced Morphine withdrawal signs was investigated. Results: A single injection of Verapamil proved to be effective in inhibiting some signs of Morphine withdrawal but ineffective in changing the number of jumps. The concurrent injections of Verapamil with Morphine prevented most signs of Morphine withdrawal. Conclusion: The results confirmed the crucial role of voltage-sensitive calcium channels in the adaptations that occur after long-term treatment with Morphine. Concurrent injections of Verapamil with Morphine could be used to prevent some signs of Morphine withdrawal. Keywords: Verapamil, Morphine withdrawal, Calcium antagonistshttp://jrms.mui.ac.ir/index.php/jrms/article/view/878http://jrms.mui.ac.ir/index.php/jrms/article/download/878/211