Zhu Hongwen, Lee MoonSook, Guan Fangxia, Agatsuma Soh, Scott Daniel, Fabrizio Kevin, Fienberg Allen A, Hiroi Noboru
Laboratory of Molecular Psychobiology, Albert Einstein College of Medicine, Bronx, NY, USA.
Biol Psychiatry. 2005 Dec 15;58(12):981-9. doi: 10.1016/j.biopsych.2005.05.026. Epub 2005 Aug 9.
The addictive properties of nicotine are mediated via dopaminergic pathways and their post-synaptic neurons in the striatum. Because post-synaptic neurons within the striatum contain high levels of the dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32), we hypothesized that DARPP-32 may functionally contribute to the behavioral effects of nicotine.
We examined the behavioral effects of nicotine and the phosphorylation state of DARPP-32 in wild-type (WT) and DARPP-32 knockout (KO) mice. In one experiment, we assessed voluntary nicotine intake (0-50 microg/ml) of WT and KO mice in a two-bottle choice paradigm. In a separate experiment, the motor-depressant effects of acute and repeated nicotine injections (0-.8 mg/kg, subcutaneously [SC]) were assessed. The phosphorylation of DARPP-32 at threonine34 and threonine75 were examined using Western blotting.
A heightened responsiveness to nicotine was seen in KO mice when compared with WT mice in oral intake and motor depression. The enhanced responsiveness in KO mice was not due to alterations in taste sensations, fluid intake, or blood nicotine or cotinine levels. Systemic injections of nicotine resulted in increased striatal DARPP-32 phosphorylation at threonine34 and threonine75.
DARPP-32 opposes the behavioral effects of nicotine possibly via concurrent phosphorylation at the two threonine sites.
尼古丁的成瘾特性是通过多巴胺能通路及其在纹状体中的突触后神经元介导的。由于纹状体内的突触后神经元含有高水平的32 kDa多巴胺和cAMP调节磷蛋白（DARPP - 32），我们推测DARPP - 32可能在功能上促成了尼古丁的行为效应。
我们研究了野生型（WT）和DARPP - 32基因敲除（KO）小鼠中尼古丁的行为效应以及DARPP - 32的磷酸化状态。在一个实验中，我们在双瓶选择范式中评估了WT和KO小鼠的自愿尼古丁摄入量（0 - 50微克/毫升）。在另一个单独的实验中，评估了急性和重复注射尼古丁（0 - 0.8毫克/千克，皮下注射[SC]）的运动抑制作用。使用蛋白质免疫印迹法检测DARPP - 32在苏氨酸34和苏氨酸75位点的磷酸化情况。
与WT小鼠相比，KO小鼠在口服摄入和运动抑制方面对尼古丁的反应性增强。KO小鼠反应性增强并非由于味觉感受、液体摄入或血液中尼古丁或可替宁水平的改变。全身注射尼古丁导致纹状体中DARPP - 32在苏氨酸34和苏氨酸75位点的磷酸化增加。
DARPP - 32可能通过在两个苏氨酸位点同时磷酸化来对抗尼古丁的行为效应。
