The role of dendrodendritic dopamine neurotransmission in methamphetamine abuse

描述(由申请人提供)：甲基苯丙胺(冰毒)成瘾目前是一个巨大的公共卫生问题，但目前还没有治疗药物被批准用于治疗。精神刺激成瘾是一种慢性进行性疾病，由许多持续的神经生理适应所驱动。甲基自身给药增加了神经肽神经降压素对腹侧被盖区(VTA)的多巴胺(DA)神经元的输入，该神经元广泛参与药物奖励过程。虽然文献证据和我们的初步结果表明，神经降压素降低了DA自身受体介导的信号传递，但DA D2自身受体在药物自我给药中的作用尚未被描述。我们最近发现了在研究DA自身受体和DA介导的突触传递中缺失的工具：VTA中由树突状DA神经传递直接介导的抑制性突触后电流(或IPSC)。DA IPSC的识别首次使我们能够直接解决有关冰毒滥用和DA神经传递之间的关系的突触问题。这个应用程序的目标是确定DA细胞体水平上的关键突触适应，这些适应负责冰毒自我给药的升级。我们的中心假设是，冰毒的使用通过神经降压素依赖的细胞内钙升高，导致冰毒自我给药行为的升级，减少了VTA DA神经元中的D2自身受体信号。我们将通过结合脑片上的膜片钳电生理学和静脉注射冰毒以及小鼠VTA部位特异性药物注射来测试这一点。目标1中的研究将确定导致DA IPSC长期抑郁的机制。需要检验的假设是，DA ipscs的长期抑制是由神经降压素受体依赖的细胞内钙升高引起的，产生蛋白磷酸酶3的激活。目标2中的研究将确定冰毒自我给药产生的DA ipscs的变化。需要检验的假设是，体内随机给药通过神经降压素依赖的机制减少了自身受体信号。目标3中的研究将确定DA自身受体介导的神经传递在冰毒自我给药升级中的作用。需要检验的假设是，自身受体信号直接限制冰毒摄入量，神经降压素诱导的这一信号的抑制有助于长期使用药物观察到的自我给药的升级。这些研究的结果将确定导致自身受体信号减少的关键细胞机制，并将确定这种树突状DA神经传递的减少如何导致冰毒自我给药的升级。这些发现将提供对神经降压素、DA神经元活性和冰毒自我给药之间关系的详细了解，并将为针对神经降压素和自身受体介导的信号转导的治疗奠定基础。

DESCRIPTION (provided by applicant): Methamphetamine (METH) addiction currently presents an enormous public health issue, and yet no therapeutic agent is currently approved for its treatment. Psychostimulant addiction is a chronic, progressive disease driven by numerous persistent neurophysiological adaptations. METH self-administration increases input of the neuropeptide neurotensin onto dopamine (DA) neurons in the ventral tegmental area (VTA), which are extensively implicated in drug reward processes. While literature evidence and our preliminary results suggest that neurotensin decreases DA autoreceptor-mediated signaling, the role of DA D2 autoreceptors in drug self-administration has not been described. We have recently identified what had been a missing tool in the study of DA autoreceptors and DA-mediated synaptic transmission: an inhibitory postsynaptic current (or IPSC) mediated directly by dendrodendritic DA neurotransmission in the VTA. The identification of the DA IPSC allows us, for the first time, to directly address synaptic questions concerning the relationship between METH abuse and DA neurotransmission. The goal of this application is to determine key synaptic adaptations at the level of the DA cell body that are responsible for escalating METH self-administration. Our central hypothesis is that METH use decreases D2 autoreceptor signaling in VTA DA neurons through a neurotensin-dependent rise in intracellular calcium, producing an escalation of METH self-administration behavior. We will test this by combining patch clamp electrophysiology in brain slices with intravenous METH self-administration and VTA site-specific drug microinjections in mice. The studies in Aim 1 will determine the mechanisms responsible for long-term depression of the DA IPSC. The hypothesis to be tested is that that long term depression of DA IPSCs is produced by a neurotensin receptor-dependent rise in intracellular calcium producing the activation of protein phosphatase 3. The studies in Aim 2 will determine the changes in the DA IPSC produced by METH self-administration. The hypothesis to be tested is that in vivo contingent METH self-administration decreases autoreceptor signaling through a neurotensin-dependent mechanism. The studies in Aim 3 will determine the role of DA autoreceptor-mediated neurotransmission on the escalation of METH self-administration. The hypothesis to be tested is that autoreceptor signaling directly limits METH intake, and that neurotensin-induced depression of this signal contributes to the escalation of self-administration observed with prolonged access to the drug. The results of these studies will identify key cellular mechanisms responsible for decreased autoreceptor signaling, and will determine how this decrease in dendrodendritic DA neurotransmission produces escalation of METH self-administration. These findings will provide a detailed understanding of the relationship between neurotensin, DA neuron activity and METH self-administration and will lay the foundation for therapeutics targeting neurotensin- and autoreceptor-mediated signaling.