Latrophilin-3 and ADHD: A new potential mechanism

注意力缺陷多动障碍（ADHD）影响540万儿童，每年花费超过720亿美元，但其病因学知之甚少。一种孤儿受体的新基因已经被发现，它具有ADHD的高风险：Latrophilin-3（LPHN 3）。我们有一个新的Lphn 3敲除（KO）大鼠。这只老鼠表现出过度活跃和过度反应。但多动症也会影响注意力和冲动控制。目的-1将测试Lphn 3 KO大鼠的注意力和抑制控制。多动症是用兴奋剂治疗的，兴奋剂可以增加注意力，减少注意力分散和活动。目的-2是测试ADHD药物在Lphn 3 KO大鼠中的作用。有效的ADHD药物通过作用于单胺再摄取和释放过程或受体来增加多巴胺和去甲肾上腺素信号（一些增加5 HT）。目的-3是确定Lphn 3破坏对单胺，转运蛋白和受体的影响。总体目的是确定Lphn 3对ADHD的行为和神经化学表型的贡献。拟议的实验将产生Lphn 3如何促进与ADHD相关的每种症状和神经化学变化的基本数据。Lphn 3可能成为开发调节Lphn 3功能或其结合伴侣（Flrt 3）以减轻ADHD潜在缺陷的药物的新靶点。因此，这代表了对ADHD原因的创新研究。我们是唯一具有Lphn 3 KO大鼠和中试表型数据的组。因此，我们处于独特的地位，可以追求这种模式。特异性Aim-1将决定Lphn 3 KO大鼠的ADHD样表型。将评估Lphn 3功能丧失在延长的运动活动、感觉运动门控、认知灵活性/注意力（集合转移）、注意力/灵活性（连续性能测试）、工作记忆和对ADHD药物的反应中的作用。数据将证明ADHD表型的范围和严重程度。Specific Aim-2将阐明Lphn 3 KO大鼠的神经化学变化。实验-2a：通过免疫组织化学比较KO和WT大鼠与ADHD相关的单胺（多巴胺（通过酪氨酸羟化酶）、5 HT和多巴胺β羟化酶（对于NE））的变化，并作为对照GAD 67（对于GABA）和NMDA-NR 1（对于谷氨酸）。将对每种转运蛋白进行染色。由于多巴胺D4和5 HT 2B受体与ADHD有关，因此也将对其进行评估。Exp-2b：一旦确定了组织学变化区域，其他动物将通过Western印迹分析这些区域。实验-2c：一旦来自Aim-2b的蛋白质印迹识别出显著变化，这将用于指导在行为测试后在动物的Aim-2c中分析哪些标志物;然后将进行神经化学和行为数据之间的相关性。此外，将进行Flrt 3的RT-PCR，以确定其是否因Lphn 3突变而改变。这些实验将极大地推进ADHD研究领域。

DESCRIPTION (provided by applicant): Attention Deficit Hyperactivity Disorder (ADHD) affects 5.4 million children at a cost >$72 billion/year, yet its etiology is poorly understood. A new gene for an orphan receptor has been identified that conveys high risk for ADHD: Latrophilin-3 (LPHN3). We have a new Lphn3 knock-out (KO) rat. This rat shows hyperactivity and hyper-reactivity. But ADHD also affects attention and impulse control. Objective-1 will test Lphn3 KO rats for attention and inhibitory control. ADHD is treated with stimulants, which increase attention and reduce distractibility and activity. Objective-2 is to test the effects of ADHD medications in Lphn3 KO rats. Effective ADHD medications increase dopamine and norepinephrine signaling (and some increase 5HT) by acting on monoamine reuptake and release processes or receptors. Objective-3 is to determine the effects of Lphn3 disruption on monoamines, transporters, and receptors. The overall purpose is to identify the contribution of Lphn3 to the behavioral and neurochemical phenotype of ADHD. The proposed experiments will generate essential data for how Lphn3 contributes to each of the symptoms and neurochemical changes associated with ADHD. Lphn3 could become a novel target for development of drugs that modulate Lphn3 function or its binding partner (Flrt3) to alleviate the underlying deficit in ADHD. As such this represents innovative research on a cause of ADHD. We are the only group with the Lphn3 KO rat and pilot phenotypic data. Therefore, we are uniquely position to pursue this model. Specific Aim-1 will determine the ADHD-like phenotype of Lphn3 KO rats. The role of Lphn3 loss of function in extended locomotor activity, sensorimotor gating, cognitive flexibility/attention (set shifting), attention/flexibility (continuous performance test), working memory, and response to ADHD medications will be assessed. The data will demonstrate the range and severity of ADHD phenotype. Specific Aim-2 will elucidate the neurochemical changes in Lphn3 KO rats. Exp-2a: KO and WT rats will be compared by immunohistochemistry for changes in monoamines implicated in ADHD (dopamine (by tyrosine hydroxylase), 5HT, and dopamine beta hydroxylase (for NE), and as controls GAD67 (for GABA) and NMDA-NR1 (for glutamate). Stains for each transporter will be performed. Because the dopamine D4 and 5HT2B receptors have been implicated in ADHD they will also be assessed. Exp-2b: Once histological regions of change are identified, other animals will have these regions analyzed by Western blot. Exp-2c: Once Westerns from Aim-2b identify significant changes, this will be used to guide which markers will be analyzed in Aim-2c in animals after behavioral testing; then correlations between neurochemical and behavioral data will be performed. In addition, RT-PCR for Flrt3 will be performed to determine it is altered by the Lphn3 mutation. These experiments will materially advance the field of ADHD research.