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

项目总结 学习障碍是胎儿酒精谱患者最常见的行为缺陷 精神障碍(FASD)。目前，还没有确定的临床有效的药物治疗干预措施 这些行为问题。利用一种成熟的FASD大鼠模型，我们已经报道了组胺 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方面。我们还观察到H3受体-效应器偶联增加和 增强H3受体对PAE大鼠齿状回谷氨酸释放的抑制作用。 总之，这些结果表明，PAE增加了H3受体介导的谷氨酸释放的抑制和 ABT-239降低了这种增强的抑制影响。一个关于PAE大鼠为什么 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受体与rH3C亚型相关。这一假定的转变将使人们对 组胺H3受体激动剂对PAE大鼠的抑制作用。这项NMARC研究的主要目标 组件的应用是：1)检测PAE是否增加了rH3A相对于rH3C的表达 内嗅皮质神经元投射到齿状回。2)更彻底地确定 PAE诱导的H3受体-效应偶联增强及第二种H3受体反向激动剂的作用 拮抗剂SAR152954对H3受体介导的谷氨酸能神经传递的抑制作用 齿状回。在特定的目标1A中，我们将使用原位杂交和qRT-PCR方法首先确认 PAE是否增加rH3A/rH3CmRNA的表达。在AIM 1B中，我们将使用[35S]-gtpS绑定 对PAE对H3受体的影响进行更详细的研究 并评估PAE大鼠相对于对照组对SAR152954的差异敏感性。具体而言 目的：我们将进行体外脑片生理学研究，以检验：1)PAE对 H3受体激动剂美西美普对基线状态下齿状回fEPSP反应和双脉冲可塑性的影响 并在Theta爆发式刺激条件下进行。2)SAR152954单独和存在的影响 美西美普对脉冲配对比率和长时程增强的影响。在目标2B中，我们将研究PAE对以下方面的影响 清醒自由活动大鼠高频刺激前后fEPSP和PPR的变化我们预测 SAR152954可改善H3受体介导的大鼠突触可塑性抑制 不损害对照组大鼠突触传递的浓度/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 并致力于建立治疗PAE的新干预措施的机制基础-- 导致突触可塑性和记忆缺陷。这些研究可以为临床前研究提供额外的依据 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