Zhu Jun, Apparsundaram Subbu, Dwoskin Linda P
College of Pharmacy, University of Kentucky, Lexington, KY 40536, USA.
J Pharmacol Exp Ther. 2009 Mar;328(3):931-9. doi: 10.1124/jpet.108.147025. Epub 2008 Dec 16.
Previous research shows that nicotine increases dopamine (DA) clearance in rat prefrontal cortex (PFC) and striatum via a nicotinic receptor (nAChR)-mediated mechanism. The present study investigated whether activation of nAChRs regulates DA transporter (DAT) function through a trafficking-dependent mechanism. After nicotine administration (0, 0.3, and 0.8 mg/kg s.c., 15-1440 min after injection), DAT function and trafficking in synaptosomes of PFC and striatum were determined. nAChR mediation of the effect of nicotine on DAT function and trafficking in PFC was determined by pretreatment with mecamylamine, dihydro-beta-erythroidine, or methyllycaconitine. Nicotine (0.8 mg/kg, 15 and 30 min after injection) increased the maximal velocity (V(max)) of [3H]DA uptake in PFC with no change in K(m), compared with control. Biotinylation and Western blot assays showed that nicotine (0.8 mg/kg; 30 min) increased DAT cell surface expression in PFC. In contrast, a lower dose of nicotine (0.3 mg/kg; 30 min) did not alter DAT function and trafficking in PFC. Pretreatment with mecamylamine, dihydro-beta-erythroidine, or methyllycaconitine (1.5, 8.0, and 10.0 mg/kg s.c., respectively) completely blocked the nicotine-induced increase in V(max) in PFC. In addition, mecamylamine completely blocked the nicotine-induced increase in DAT cell surface expression in PFC. Nicotine did not increase DAT function and cell surface expression in striatum, indicating that nicotine modulates DAT function in a brain region-specific manner. Thus, results from the present study suggest that the nicotine-induced increases in DAT function and cell surface expression in PFC may mediate some of the behavioral effects of nicotine.
先前的研究表明，尼古丁通过烟碱型受体（nAChR）介导的机制增加大鼠前额叶皮质（PFC）和纹状体中多巴胺（DA）的清除率。本研究调查了nAChRs的激活是否通过一种依赖于转运的机制调节多巴胺转运体（DAT）的功能。给予尼古丁（0、0.3和0.8mg/kg皮下注射，注射后15 - 1440分钟）后，测定PFC和纹状体突触体中DAT的功能和转运情况。通过用美加明、二氢β-刺桐啶或甲基牛扁亭预处理来确定nAChR对尼古丁在PFC中对DAT功能和转运作用的介导。与对照组相比，尼古丁（0.8mg/kg，注射后15和30分钟）增加了PFC中[3H]DA摄取的最大速度（V(max)），而K(m)没有变化。生物素化和蛋白质印迹分析表明，尼古丁（0.8mg/kg；30分钟）增加了PFC中DAT的细胞表面表达。相比之下，较低剂量的尼古丁（0.3mg/kg；30分钟）并未改变PFC中DAT的功能和转运。用美加明、二氢β-刺桐啶或甲基牛扁亭（分别为1.5、8.0和10.0mg/kg皮下注射）预处理完全阻断了尼古丁诱导的PFC中V(max)的增加。此外，美加明完全阻断了尼古丁诱导的PFC中DAT细胞表面表达的增加。尼古丁并未增加纹状体中DAT的功能和细胞表面表达，表明尼古丁以脑区特异性方式调节DAT功能。因此，本研究结果表明，尼古丁诱导的PFC中DAT功能和细胞表面表达的增加可能介导了尼古丁的一些行为效应。
