Alpha-2 agonists decrease expression of morphine-induced conditioned place preference

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• 作者：Morteza Samini ; Ayda Kardan ; Shahram Ejtemaei Mehr
• 关键词：Morphine ; Clonidine ; Tizanidine ; Xylazine ; Conditioned place preference ; ID₅₀
• 刊名：Pharmacology Biochemistry and Behavior
• 出版年：2008
• 期刊代码：219_00913057
• 类别：med
• 出版时间：February 2008
• 卷：88
• 期：4
• 页码：403-406
• 文件大小：194 K

摘要

Opioidergic system can interact with different transmission such as dopaminergic and adrenergic system. It has been shown that α-adrenergic system is involved in some effects of opioid including reward. In this study, alpha-2 agonists were used before testing on day 6 to evaluate their effects on the expression of morphine-induced conditioned place preference (CPP). Our results showed that intraperitoneal (ip) injections of morphine (5 mg/kg) induced CPP. Administration of α₂-agonists clonidine (0.01, 0.02 and 0.04 mg/kg, ip), tizanidine (0.1, 0.2 and 0.4 mg/kg, ip) and xylazine (2.5, 5 and 10 mg/kg, ip) decreases the expression of morphine-induced CPP. Yohimbine (0.5 mg/kg, ip) reversed the inhibitory effect of α₂-agonists. The comparison of potency of inhibitory effect of three agonists showed that ID₅₀ values for clonidine, tizanidine and xylazine were 0.013, 0.32 and 1.86 mg/kg respectively. Therefore, it is concluded that α₂-agonists decrease the morphine-induced CPP in mice and clonidine is more potent than tizanidine and xylazine. The relative potency of clonidine with respect to tizanidine and xylazine was 30 and 180 respectively.