GABA B MECHANISMS OF ABSENCE SEIZURES IN LETHARGIC MICE

GABA B 昏睡小鼠失神发作的机制

• 批准号: 2669014
• 负责人: DAVID A HOSFORD
• 金额: $ 14.98万
• 依托单位: DUKE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-05-01 至 1999-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2669014
• 关键词: GABA receptor; electroencephalography; epilepsy; laboratory mouse; microelectrodes; muscle relaxants; neocortex; neurons; neuropharmacology; pyramidal cells; synaptosomes; thalamus; voltage /patch clamp

Absence seizures afflict a significant percentage of children with epilepsy. Attempts to understand the molecular mechanisms of absence seizures may be facilitated by studying animal models. Our earlier studies using the lethargic (lh/lh) mutant mouse model of absence seizures showed: i) an apparent requirement for GABAB receptors in absence seizures; ii) an increased number of GABAB receptors in neocortex and thalamic nuclei compared to control (+/+) mice; iii) no change in electrophysiologic responses mediated by postsynaptic GABAB receptors in thalamic neurons in lh/lh compared to +/+ mice; and iv) alterations in biochemical functions mediated by presynaptic GABAB receptors in neocortex and thalamus in lh/lh compared to +/+ mice. The short-term goals of this proposal are to seek physiologic correlates to our findings regarding GABAB responses in lh/lh and +/+ mice, and to determine if these responses cause absence seizures. We will perform 6 specific aims to answer the following questions. First (aims 1-3)), what is the physiologic correlate of our evidence that presynaptic GABAB receptor-mediated function is altered in thalamic and neocortical neurons from lh/lh mice? Second (aims 4 and 5), is the altered function mediated by presynaptic GABAB receptors in lh/lh mice caused by the increased numbers of GABAB receptors in these mice? Third (aim 6), are absence seizures in lh/lh mice caused by the increased numbers of GABAB receptors in these mice? In the long-term, the answers forthcoming will increase our understanding of the physiologic and pathophysiologic roles of GABAB receptor-mediated function. More importantly, this information may lead to better therapies for patients with absence seizures. In specific aims 1 and 2 we will use Cs+-filled microelectrodes and whole- cell voltage-clamp techniques in ventrobasal (VB) thalamic neurons (aim 1) or neocortical pyramidal neurons (aim 2) of lh/lh and +/_ slices to measure the effect of presynaptic GABAB receptor activation on IPSCs (autoreceptor function) and EPSCs (heteroreceptor function) evoked by local stimulation. We will activate presynaptic GABAB receptors by: i) applying the GABAB receptor agonist (-) baclofen to the bath; and ii) measuring paired-pulse and homosynaptic depression. In specific aim 3 we will use Cs+ filled microelectrodes and whole-cell voltage clamp techniques in VB thalamic neurons to measure the effect of presynaptic GABAB receptor activation on spindles evoked by stimulation of nucleus reticularis thalami (NRT). In specific aim 4 we will down-regulate GABAB receptors in lh/lh mice by chronic administration of GABAB receptor agonists. We will then measure the effect of presynaptic GABAB receptors on [3H]-GABA release in thalamic and neocortical synaptosomes from these mice and from "normal" lh/lh mice. In specific aim 5 we will use whole-cell voltage-clamp techniques in VB thalamic neurons of down-regulated lh/lh mice to measure the effect of presynaptic GABAB receptors on spindles evoked by stimulation of NRT. In specific aim 6 we will implant bipolar recording electrodes into neocortex of +/+ and lh/lh mice. After up-regulating GABAB receptors by chronic administration of GABAB antagonists to half of the +/+ mice, we will use EEG recordings to compare absence seizure frequency in the groups.

失神发作困扰着相当大比例的儿童， 癫痫。试图理解缺失的分子机制 通过研究动物模型可以促进癫痫发作。我们早期的研究 使用昏睡(黄体生成素/黄体生成素)突变小鼠失神发作模型显示： 一)失神发作时对GABAB受体的明显要求；二)和 新皮质和丘脑核团GABAB受体数目增加 与对照组(+/+)小鼠比较；iii)电生理无变化 突触后GABAB受体介导的丘脑神经元反应 黄体生成素/黄体生成素与+/+小鼠的比较；以及iv)生化功能的改变 促黄体生成素/促黄体生成素突触前GABAB受体介导的新皮质和丘脑 与+/+小鼠相比。 这项提议的短期目标是寻找与 我们关于黄体生成素/黄体生成素和+/+小鼠的GABAB反应的研究结果，以及 确定这些反应是否会导致缺勤发作。我们将演出6场 具体旨在回答以下问题。第一(目标1-3))，什么 我们的证据与突触前GABAB的生理学关联 丘脑和新皮质神经元中受体介导的功能改变 来自黄体生成素/黄体生成素小鼠？第二个(目标4和5)，是改变的功能介导的吗 由突触前GABAB受体引起的促黄体生成素/促黄体生成素小鼠 这些小鼠体内GABAB受体的数量？第三(目标6)，缺席 GABAB受体数目增加引起黄体生成素/黄体生成素小鼠癫痫发作 在这些老鼠身上？从长远来看，即将到来的答案将增加我们的 对GABAB的生理和病理生理作用的认识 受体介导的功能。更重要的是，这些信息可能会导致 更好的治疗失神发作的方法。 在具体目标1和2中，我们将使用填充Cs+的微电极和整体- 丘脑腹基底区神经元的细胞电压钳技术(目标1) 或对黄体生成素/黄体生成素和+/_脑片新皮质锥体神经元(目标2)进行测量 突触前GABAB受体激活对IPSCs的影响 功能)和由局部刺激引起的EPSCs(异型受体功能)。 我们将通过以下方式激活突触前GABAB受体：i)应用GABAB 受体激动剂(-)巴氯芬；以及ii)测量成对脉冲 以及同型突触抑郁。 在具体目标3中，我们将使用Cs+填充的微电极和全细胞 电压钳技术在Vb丘脑神经元检测中的作用 电刺激诱发的纺锤体突触前GABAB受体激活 丘脑网状核(NRT)。 在特定目标4中，我们将通过以下方式下调促黄体生成素/促黄体生成素受体 长期服用GABAB受体激动剂。然后我们将测量 突触前GABAB受体对丘脑[~3H]-GABA释放的影响 以及来自这些小鼠和“正常”的黄体生成素/黄体生成素小鼠的新皮质突触体。 在具体目标5中，我们将在VB中使用全单元电压钳位技术 下调黄体生成素/黄体生成素对小鼠丘脑神经元的影响 刺激NRT诱发的纺锤体突触前GABAB受体。 在特定的目标6中，我们将把双极记录电极植入 +/+和黄体生成素/黄体生成素小鼠新皮质。在上调GABAB受体后 对一半的+/+小鼠长期给予GABAB拮抗剂 将使用脑电记录来比较这两组人的失神发作频率。

项目成果

Studies of the lethargic (lh/lh) mouse model of absence seizures: regulatory mechanisms and identification of the lh gene.

失神发作昏睡 (lh/lh) 小鼠模型的研究：调节机制和 lh 基因的鉴定。

• 发表时间: 1999
• 期刊: Advances in neurology.
• 作者: Hosford,DA;Lin,FH;Wang,Y;Caddick,SJ;Rees,M;Parkinson,NJ;Barclay,J;Cox,RD;Gardiner,RM;Hosford,DA;Denton,P;Wang,Y;Seldin,MF;Chen,B
• 通讯作者: Chen,B

Characterization of the antiabsence effects of SCH 50911, a GABA-B receptor antagonist, in the lethargic mouse, gamma-hydroxybutyrate, and pentylenetetrazole models.

SCH 50911（一种 GABA-B 受体拮抗剂）在昏睡小鼠、γ-羟基丁酸盐和戊四唑模型中的抗失神作用的表征。

• 发表时间: 1995
• 期刊: The Journal of pharmacology and experimental therapeutics.
• 作者: Hosford,DA;Wang,Y;Liu,CC;Snead3rd,OC
• 通讯作者: Snead3rd,OC

Generalized epilepsies: emerging insights into cellular and genetic mechanisms.

全身性癫痫：对细胞和遗传机制的新见解。

• 发表时间: 1997
• 期刊: Current opinion in neurology
• 影响因子: 4.8
• 作者: Hosford,DA;Caddick,SJ;Lin,FH
• 通讯作者: Lin,FH