D3 Dopamine receptor signaling in the regulation of startle gating

描述(由申请人提供)： 几乎所有被批准的治疗精神分裂症的药物都是混合的多巴胺(DA)D2家族(D2，3和4)受体拮抗剂或部分激动剂，如果有的话，对特定亚型的D2受体有有限的偏好。选择性D3拮抗剂可能代表了一类新的抗精神病药物，它没有非选择性拮抗剂的主要副作用。抗精神病药物作用的一个有价值的、翻译的和预测的模型是脉冲前抑制(PPI)，这是一种感觉运动门控的操作措施，在未用药的精神分裂症患者中受损。这项应用的长期目标是确定药物发现的分子靶点，并通过表征调节感觉运动门控的D3受体激活的细胞内信号通路，将体内和体外的药理治疗试验联系起来。第一个目的是确定D3受体激活对大鼠的行为影响。优先的D3激动剂，如普拉克索(PRA)PD128907或7-OH-DPAT将单独或在D3选择性拮抗剂SB277,011或D2选择性拮抗剂L741,626之后给药。将测量激动剂诱导的PPI和其他行为的变化，D2和D3受体的作用将通过它们与选择性拮抗剂的阻断以及与D2选择性激动剂苏马尼罗的比较来确定。基于这些数据，最具D3特异性的激动剂和剂量将用于Aim 2的后续研究。第二个目标是确定D3受体激活对大鼠细胞内的影响。伏核(NAC)中DA连接的信号转导分子将被检测：GTP3S结合、腺苷环化酶活性、PKA活性、CREB磷酸化、c-fos表达、ERK1/2活性、MSK1活性和ELK-1水平。检测的顺序将允许对目标信号通路进行最有效的评估。为了进行比较，还将测量背侧纹状体中的信号分子水平。第三个目的是测试Aim 2中确定的信号分子在Aim 1中确定的D3介导的行为效应中的作用，方法是通过脑内注射相关通路的抑制物或激活剂来改变信号级联活动。适合于cAMP/PKA途径的一个例子是在PPI检测之前在NAC内输注RP-cAMP(一种cAMP结合的竞争性抑制剂)。对cAMP/PKA或MAPK/ERK通路“下游”的干预将包括在NAC内注入CREB反义寡核苷酸。阐明控制PPI的D2和D3调节的信号通路中的差异对于指导基于推理的新型抗精神病药物的开发具有翻译潜力。此外，介导PPI缺陷的信号分子可能与精神分裂症和相关疾病的病理生理学有关，因此，拟议的研究将为神经精神病学遗传连锁研究中确定的基因提供生理背景。 公共卫生相关性： 项目叙事精神分裂症是一种慢性、严重的、使人衰弱的大脑疾病，在美国和世界范围内影响着大约1%的人口，症状通常在成年早期开始。关于这种疾病，我们还有很多需要了解的地方，但有希望的新研究将大脑化学变化与严重症状联系起来，可能会通过开发更有效、副作用更少的新药来改善对精神分裂症患者的护理。通过我们的研究，我们希望扩大我们对与精神分裂症相关的生物系统的了解，并将这些进展直接应用于改善患者的治疗选择。

DESCRIPTION (provided by applicant): Virtually all approved medications for schizophrenia are mixed dopamine (DA) D2-family (D2, 3 and 4) receptor antagonists or partial agonists with limited - if any - preference for specific subtypes of D2-family receptors. Selective D3 antagonists may represent a novel class of antipsychotics that lack the major side effects of non- selective antagonists. One valuable, translational and predictive model for antipsychotic action is prepulse inhibition (PPI), an operational measure of sensorimotor gating, that is impaired in unmedicated schizophrenia patients. The long term goals of this application are to identify molecular targets for drug discovery and link in vivo and ex vivo assays of pharmacological treatments by characterizing the intracellular signaling pathways of D3 receptor activation that regulate sensorimotor gating. The first aim is to determine the behavioral effects of D3 receptor activation in the rat. Preferential D3 agonists such as pramipexole (PRA) PD128907, or 7-OH- DPAT will be administered alone or after either SB277,011, a D3-selective antagonist, or L741,626, a D2- selective antagonist. Agonist-induced changes in PPI and other behaviors will be measured, and the role of D2 vs. D3 receptors will be determined by their blockade with selective antagonists, and by comparison with the D2-selective agonist, sumanirole. Based on these data, the most D3-specific agonist and dose will be used for subsequent studies in Aim 2. The second aim is to determine the intracellular effects of D3 receptor activation in the rat. DA-linked signal transduction molecules in the nucleus accumbens (NAC) will be assayed for: GTP3S binding, adenylate cyclase activity, PKA activity, CREB phosporylation, c-fos expression, ERK1/2 activity, MSK1 activity, and Elk-1 levels. The order of assays will permit the most efficient assessment of the the targeted signal pathways. Signaling molecule levels will also be measured in the dorsal striatum for comparison. The third aim is to test the role of signaling molecules identified in Aim 2 in D3-mediated behavioral effects identified in Aim 1 by altering signaling cascade activity via intracerebral infusion of inhibitors or activators of the relevant pathways. An example appropriate for the cAMP/PKA pathway would involve intra- NAC infusion of Rp-cAMPS (a competitive inhibitor of cAMP binding) prior to PPI testing. An intervention "downstream" of either the cAMP/PKA or MAPK/ERK pathways would be involve intra-NAC infusion of CREB antisense oligonucleotide. Clarifying the divergence in signaling pathways that control D2- and D3-regulation of PPI has translational potential for guiding the development of novel inference-based antipsychotics. Furthermore, signaling molecules that mediate PPI deficits might be linked to the pathophysiology of schizophrenia and related disorders, and thus the proposed study would provide a physiological context for genes identified in neuropsychiatric genetic linkage studies. PUBLIC HEALTH RELEVANCE: Project Narrative Schizophrenia is a chronic, severe, debilitating brain disorder that affects about 1% of the population in the U.S. and worldwide, with symptoms usually beginning in early adulthood. We still have much to learn about this disorder, but promising new research linking changes in brain chemistry with severe symptoms may lead to improvements in care for schizophrenia patients, through the development of new medications with greater efficacy and fewer side effects. Through our studies, we hope to expand our understanding of biological systems related to schizophrenia and to apply these advancements directly towards improving the treatment options for patients.