Neural Actions of Toluene

描述(申请人提供)：使用挥发性有机溶剂作为滥用药物是一个重要的健康问题。这些药物通常被称为滥用吸入剂，因其醉人效应而被自愿吸入或“吸入”。滥用吸入剂的使用在儿童和青少年中尤其普遍，因为这些化合物是合法的，存在于包括胶水、粘合剂和油漆稀释剂在内的各种家用和商业产品中。滥用吸入剂与各种不良反应有关，包括学习成绩下降、大脑异常以及因溶剂引起的心律失常而导致的猝死综合征。尽管滥用吸入剂会产生类似酒精的中毒迹象，但其作用部位和作用机制在很大程度上尚不清楚。在该项目之前的资助期内开展的研究使用了重组表达技术和电生理学来研究滥用吸入剂对脑神经元广泛表达的离子通道的影响。这些研究的结果显示，滥用吸入剂对调节神经元兴奋性的电压门控和配体门控离子通道的影响具有惊人的选择性。特别是，NR1/2B NMDA受体和1422烟碱型乙酰胆碱受体是被发现的最敏感的通道。在这一应用中，我们着重于这些通道在调节甲苯(滥用吸入剂的原型)对三个已知在调节药物滥用影响的大脑区域内的主要神经元活动中所起的作用。用全细胞膜片钳电生理学方法研究甲苯对大鼠腹侧被盖区(VTA)、伏核中棘神经元(NAcc)和前额叶皮质(PFC)深层锥体神经元的影响。目的1将测定成瘾神经回路中NMDA EPSCs对甲苯的敏感性，特别关注NR1/2B受体。目的2将确定急性甲苯对VTA DA神经元兴奋性的影响，特别关注1422个nAChRs。目的3将使用一种新的三层共培养系统来确定甲苯对NR1/2B和1422个nAChRs的影响，这些nAChRs介导由PFC神经元产生的复杂放电模式。最后，Aim 4将测试这一假说，即体内暴露于甲苯会导致体外测量的谷氨酸能突触可塑性指标的变化。这些研究的结果将填补我们知识的一个重要空白，并将确定甲苯对成瘾神经回路关键元素的作用。与公共健康相关滥用吸入剂是一类重要的滥用药物，其作用机制受到的关注相对较少。这项提案中将要进行的研究将详细分析滥用吸入剂对涉及成瘾的脑区神经元的影响。

DESCRIPTION (provided by applicant): The use of volatile organic solvents as drugs of abuse is an important health problem. These agents, often termed abused inhalants, are voluntarily inhaled or "huffed" for their intoxicating effects. The use of abused inhalants is especially prevalent among children and adolescents since these compounds are legal and are found in a wide variety of household and commercial products including glues, adhesives and paint thinners. Abused inhalants are associated with a variety of adverse effects ranging from reduced academic performance, brain abnormalities and a sudden-death syndrome resulting from solvent-induced cardiac arrhythmia. Although abused inhalants produce ethanol-like signs of intoxication, their sites and mechanisms of action that underlie these effects are largely unknown. Research carried out during the previous funding period of this project used recombinant expression techniques and electrophysiology to study the effects of abused inhalants on ion channels widely expressed by brain neurons. Results from these studies revealed a surprising degree of selectivity for the effects of abused inhalants on both voltage-gated and ligand-gated ion channels that regulate neuronal excitability. In particular, the NR1/2B NMDA receptors and the 1422 nicotinic acetylcholine receptor were among the most sensitive channels identified. In this application, we focus on the role that these channels play in mediating the effects of toluene, the prototype abused inhalant, on the activity of principal neurons within three brain regions known to be important in mediating the effects of drugs of abuse. Whole-cell patch-clamp electrophysiology will be used to study the effects of toluene on dopamine neurons of the ventral tegmental area (VTA), medium spiny neurons of the nucleus accumbens (NAcc) and deep-layer pyramidal neurons of the prefrontal cortex (PFC). Aim 1 will determine the toluene sensitivity of NMDA EPSCs within the addiction neurocircuitry with a special focus on NR1/2B receptors. Aim 2 will determine the effect of acute toluene on VTA DA neuron excitability with a special focus on 1422 nAchRs. Aim 3 will use a novel triple-slice co-culture system to determine the effects of toluene on NR1/2B and 1422 nAchRs that mediate complex firing patterns produced by PFC neurons. Finally, Aim 4 will test the hypothesis that exposure to toluene in vivo induces changes in indicators of plasticity in glutamatergic synapses measured in vitro. Results from these studies will fill an important gap in our knowledge and will define the actions of toluene on key elements of the addiction neurocircuitry. PUBLIC HEALTH RELEVANCE Abused inhalants are an important class of drugs of abuse that have received relatively little attention with respect to their mechanisms of action. Research to be carried out in this proposal will provide a detailed analysis of the effects of abused inhalants on neurons within brain areas involved in addiction.