Fetal Ethanol Effects on Histaminergic Regulation of Neurotransmission

描述(由申请人提供)：学习障碍是胎儿酒精谱系障碍儿童最常见的行为缺陷。为这些残疾开发有效的药物治疗干预措施，需要更清楚地了解胎儿酒精引起的学习障碍的神经生物学基础，并随后识别其作用机制将被预测为具有临床实用价值的治疗剂。我们已经观察到组胺H3受体拮抗剂ABT-239改善了乙醇诱导的胎儿齿状回长时程增强(LTP)和学习能力的缺陷。我们还观察到酒精胎鼠的齿状回H3受体-效应器偶联增加。鉴于突触前H3受体抑制谷氨酸的释放，我们的结果表明，胎儿酒精暴露增加了H3受体介导的谷氨酸释放的抑制，而ABT-239减少了这种增强的抑制影响。我们假设：胎儿酒精暴露提高了齿状回突触前组胺H3受体的功能。这种高度的抑制作用减少了穿通通路-齿状颗粒细胞突触的谷氨酸释放，进而导致LTP的缺陷和齿状回对功能损伤敏感的习得行为。为了验证这一假设，我们的具体目标将检验：1：[~3H]-A349821，一种选择性的H3受体拮抗剂，在齿状回中的结合，以定量对照和胎儿酒精后代的H3受体密度(目标1A)。我们还将使用选择性H3受体激动剂甲硫美辛进行[~3H]-A349821的甲基美芬置换结合研究，以确定H3受体高亲和力和低亲和力激动剂结合位点的比例(AIM 1B)，并通过测量甲基美芬刺激的[35S]-GTPgS结合(AIM 1C)来检测H3受体-效应器的偶联。2：通过测量双脉冲可塑性和微小突触后电流，以及这两种药物对对照组和酒精暴露胎儿子代穿透路径齿状颗粒细胞突触LTP的影响，研究美施匹普和ABT-239对谷氨酸和GABA释放的影响。3：美施美普和ABT-239对乙醇暴露仔鼠体内穿孔通路-颗粒细胞突触的双脉冲可塑性和LTP的影响。4：美西美普对一次性情境恐惧条件反射(目标4A)和空间导航(目标4B)的影响，以及美西美普和ABT-239对对照组和酒精暴露胎儿子代的放射状臂迷宫的空间模式分离变体(目标4C)的影响。我们预计，这些研究将为胎儿酒精暴露对组胺能调节谷氨酸能神经传递和齿状回突触可塑性的影响提供重要的新见解。此外，这些结果可能为考虑将作为H3受体拮抗剂的药物作为治疗FASD患者学习障碍的假定治疗剂提供临床前药理学基础。

DESCRIPTION (provided by applicant): Learning disabilities are the most common behavioral deficit observed in children with Fetal Alcohol Spectrum Disorder. The development of effective pharmacotherapeutic interventions for these disabilities requires a clearer understanding of the neurobiologic bases of fetal ethanol-induced learning deficits and subsequently, the identification of therapeutic agents whose mechanisms of action would be predicted to have clinical utility. We have observed that the histamine H3 receptor antagonist ABT-239 ameliorates fetal ethanol-induced deficits in dentate gyrus long-term potentiation (LTP) and learning. We have also observed increased H3 receptor-effector coupling in dentate gyrus of fetal ethanol offspring. Given that presynaptic H3 receptors inhibit glutamate release; our results suggest that fetal ethanol exposure increases H3 receptor-mediated inhibition of glutamate release, and that ABT-239 reduces this heightened inhibitory influence. We hypothesize that: Fetal ethanol exposure elevates presynaptic histamine H3 receptor function in dentate gyrus. This heightened inhibitory influence reduces glutamate release at the perforant path - dentate granule cell synapse which, in turn, contributes to deficits in LTP and learned behaviors sensitive to functional damage in the dentate gyrus. To test this hypothesis, our specific aims will examine: 1: The binding of [3H]-A349821, a selective H3 receptor antagonist, in dentate gyrus to quantitate H3 receptor density in control and fetal alcohol offspring (Aim 1A). We will also use the selective H3 receptor agonist methimepip to conduct methimepip-displacement of [3H]-A349821 binding studies to determine the proportion of high- and low-affinity agonist binding sites of the H3 receptor (Aim 1B) and examine H3 receptor-effector coupling by measuring methimepip-stimulated [35S]-GTPgS binding (Aim 1C). 2: The effects of methimepip and ABT-239 on glutamate and GABA release by measuring paired-pulse plasticity and miniature postsynaptic currents along with the effects of these agents on LTP at perforant path dentate granule cell synapses in control and fetal ethanol-exposed offspring. 3: The effects of methimepip and ABT-239 on paired-pulse plasticity and LTP at the perforant path - granule cell synapse in vivo in control and fetal ethanol-exposed offspring. 4: The effects of methimepip on one-trial contextual fear conditioning (Aim 4A) and spatial navigation (Aim 4B) and the effects of methimepip and ABT-239 on a spatial pattern-separation variant of the radial arm maze (Aim 4C) in control and fetal ethanol-exposed offspring. We anticipate that these studies will provide important new insights on the impact of fetal ethanol exposure on histaminergic modulation of glutamatergic neurotransmission and synaptic plasticity in the dentate gyrus. In addition, the results could provide a preclinical pharmacologic rationale for considering drugs that act as H3 receptor antagonists as putative therapeutic agents for the treatment of learning deficits in humans with FASD.