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

项目概要 学习障碍是胎儿酒精谱系患者最常见的行为缺陷 紊乱（FASD）。目前，尚无临床有效的药物治疗干预措施 这些行为问题。使用完善的 FASD 大鼠模型，我们报告说，组胺 H3 受体反向激动剂/拮抗剂 ABT-239 可改善产前酒精暴露 (PAE) 引起的缺陷 突触可塑性和学习。我们还观察到 H3 受体-效应器耦合增加，并且 H3 受体介导的对 PAE 大鼠齿状回谷氨酸释放可能性的抑制作用增强。 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影响。对 PAE 大鼠为何如此的一种简洁解释 对 H3 受体药物更敏感的是 PAE 诱导的 rH3A 亚型表达增加 组胺 H3 受体相对于 rH3C 亚型。这种假定的转变将赋予对 组胺 H3 受体激动剂对 PAE 大鼠的抑制作用。 NMARC 研究的主要目标 组件应用的目的是： 1) 检查 PAE 是否增加 rH3A 相对于 rH3C 的表达 内嗅皮层神经元投射到齿状回。 2) 更彻底地确定事件的后果 PAE 诱导的 H3 受体-效应器耦合升高和第二个 H3 受体反向激动剂的作用 / 拮抗剂，即 SAR152954，对 H3 受体介导的谷氨酸能神经传递抑制 齿状回。在具体目标 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 rH3A/rH3C mRNA 表达比。在目标 1B 中，我们将使用 [35S]-GTPS 结合 组织切片检测，更详细地检查 PAE 对 H3 受体的影响 效应器耦合并评估 PAE 大鼠相对于对照组对 SAR152954 的差异敏感性。具体来说 目标 2A，我们将进行体外切片生理学研究来检查：1）PAE 对 H3 受体激动剂甲美哌对基线下齿状回的 fEPSP 反应和对脉冲可塑性的影响 和θ爆发后的刺激条件。 2) 单独使用 SAR152954 以及存在以下物质时的影响 methimepip 对配对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刺激前后的 fEPSP 和 PPR。我们预测 SAR152954 将改善 PAE 大鼠中 H3 受体介导的突触可塑性增强抑制 不损害对照大鼠突触传递的浓度/剂量。这些研究涉及其中两个 NMARC 的三个战略目标，即增进我们对神经生物学后果的理解 PAE 的研究，以及致力于为治疗 PAE 的新干预措施建立机制基础 引起突触可塑性和记忆力的缺陷。这些研究可以提供额外的临床前理由 考虑将 SAR152954 等药物用于 FASD 患者的临床试验。 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