Impact of histamine H3 receptor agents on PAE-induced synaptic plasticity deficits in dentate gyrus

项目摘要 学习障碍是胎儿酒精谱系患者中最常见的行为缺陷 疾病（FASD）。目前，没有确定的临床有效的药物干预措施， 这些行为问题。使用一个完善的大鼠FASD模型，我们已经报道，组胺 H3受体反向激动剂/拮抗剂ABT-239改善产前酒精暴露（PAE）诱导的缺陷 在突触可塑性和学习中的作用。我们还观察到H3受体-效应物偶联增加， H3受体介导的PAE大鼠齿状回谷氨酸释放可能性抑制增强。 总的来说，这些结果表明PAE增加了H3受体介导的谷氨酸释放抑制， ABT-239降低了这种增强的抑制作用。一个简单的解释为什么PAE大鼠 对H3受体药物更敏感的是PAE诱导的rH 3A亚型表达的增加， 组胺H3受体相对于rH 3C亚型。这一假定的转变将赋予更大的敏感性， 组胺H3受体激动剂在PAE大鼠中的抑制作用。本NMARC研究的主要目标 组分应用是：1）检查PAE是否增加rH 3A相对于rH 3C的表达， 投射到齿状回的内嗅皮层神经元。2)更彻底地建立一个 PAE诱导的H3受体-效应器偶联升高和第二种H3受体反向激动剂/ 拮抗剂，即SAR 152954，对H3受体介导的对多巴胺能神经传递的抑制作用， 齿状回在Specific Aim 1A中，我们将采用原位杂交和qRT-PCR方法首先确认 PAE是否增加rH 3A/rH 3C mRNA表达比例。在目标1B中，我们将使用[35 S]-GTP结合 在组织学切片中进行测定，以更详细地检查PAE对H3受体的影响- 效应器偶联，并评估PAE大鼠相对于对照对SAR 152954的敏感性差异。在特定 目的2A，我们将进行体外切片生理学研究，以检查：1）PAE对血管内皮细胞的作用的影响。 H3受体激动剂甲氧苄啶对齿状回fEPSP反应和对脉冲可塑性的影响 以及在θ爆发刺激条件之后。2)SAR 152954单独给药和与 甲巯咪唑对双脉冲比和长时程增强的影响。在目标2B中，我们将研究PAE对 清醒自由活动大鼠高频电刺激前后fEPSP和PPR的变化我们预测 SAR 152954将改善PAE大鼠中H3受体介导的突触可塑性抑制， 在对照大鼠中，本发明的化合物具有不损害突触传递的浓度/剂量。这些研究涉及两个 NMARC的三个战略目标，即促进我们对神经生物学后果的理解 以及致力于建立治疗PAE的新型干预措施的机制基础- 导致突触可塑性和记忆力的缺陷。这些研究可为以下方面提供额外的临床前依据： 考虑在FASD患者中进行临床试验的药物，如SAR 152954。 1

PROJECT SUMMARY Learning disabilities are the most common behavioral deficit observed in patients with Fetal Alcohol Spectrum Disorder (FASD). Currently, there are no established clinically effective pharmacotherapeutic interventions for these behavioral problems. Using a well-established rat model of FASD, we have reported that the histamine H3 receptor inverse agonist / antagonist ABT-239 ameliorates prenatal alcohol exposure (PAE)-induced deficits in synaptic plasticity and learning. We have also observed increased H3 receptor-effector coupling and a heightened H3 receptor-mediated inhibition of the probability of glutamate release in dentate gyrus of PAE rats. Collectively, these results suggest that PAE increases H3 receptor-mediated inhibition of glutamate release and that ABT-239 reduces this heightened inhibitory influence. One parsimonious explanation for why PAE rats are more sensitive to H3 receptor agents is a PAE-induced increase in the expression of the rH3A isoform of histamine H3 receptors relative to the rH3C isoform. This putative shift would confer greater sensitivity to the inhibitory effects of histamine H3 receptor agonists in PAE rats. The principal objectives of this NMARC research component application are to: 1) Examine whether PAE increases the expression of rH3A relative to rH3C in entorhinal cortical neurons projecting to the dentate gyrus. 2) More thoroughly establish the consequences of a PAE-induced elevation in H3 receptor-effector coupling and the effects of second H3 receptor inverse agonist / antagonist namely, SAR152954, on H3 receptor-mediated inhibition of glutamatergic neurotransmission in dentate gyrus. In Specific Aim 1A, we will employ in situ hybridization and qRT-PCR approaches to first confirm whether PAE increases the rH3A/rH3C mRNA expression ratio. In Aim 1B, we will use a [35S]-GTPS binding assay in histological sections to conduct a more detailed examination of the effects of PAE on H3 receptor- effector coupling and assess the differential sensitivity of PAE rats to SAR152954 relative to controls. In Specific Aim 2A, we will conduct in vitro slice physiology studies to examine: 1) The impact of PAE on the effects of the H3 receptor agonist methimepip on fEPSP responses and pair-pulse plasticity in dentate gyrus, under baseline and after theta burst stimulation conditions. 2) The effects of SAR152954 alone and in the presence of methimepip on paired-pulse ratio and long-term potentiation. In Aim 2B, we will examine the impact of PAE on fEPSP and PPR before and after high frequency stimulations in awake freely moving rats. We predict that SAR152954 will ameliorate the heightened H3 receptor mediated inhibition of synaptic plasticity in PAE rats at concentrations/doses that do not impair synaptic transmission in control rats. These studies address two of the three strategic objectives of NMARC, namely advancing our understanding of the neurobiological consequences of PAE, as well as working towards establishing the mechanistic basis for novel interventions to treat of PAE- induced deficits in synaptic plasticity and memory. These studies could provide additional preclinical rational for considering drugs such as SAR152954 for clinical trials in patients with FASD. 1