GABA/ BZ RECEPTOR EXPRESSION IN A PRECEREBELLAR CIRCUIT

小脑前回路中 GABA/BZ 受体的表达

• 批准号: 2270325
• 负责人: ADRIENNE M FROSTHOLM
• 金额: $ 20.58万
• 依托单位: OHIO STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-04-01 至 1999-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2270325
• 关键词: GABA receptor; autoradiography; benzodiazepine receptor; bicuculline; calcitonin gene related peptide; cerebellar Purkinje cell; cerebral cortex; developmental neurobiology; gamma aminobutyrate; gene induction /repression; genetically modified animals; immunocytochemistry; in situ hybridization; insulinlike growth factor; laboratory mouse; neuroanatomy; neuropharmacology; olivary body; receptor binding; receptor expression; synapses

The aim of this proposal is to examine the cellular interactions underlying changes in the developmental expression of gamma aminobutyric acid/benzodiazepine (GABA-A/BZ) receptor subunit mRNAs and ligand binding sites in the murine inferior olivary nucleus. The GABA-A/BZ receptor is thought to be a pentameric chloride channel comprised of selected alpha, beta, gamma, delta and rho subunits, the majority of which have several isoforms: alpha 1-6, beta 1-4, gamma 1-4 and rho 1-2. We have shown that, of the thirteen subunit variants present in the mammalian central nervous system, the alpha 2-5, beta 3, gamma 1-2 are expressed at significant levels in the inferior olivary nucleus. Two clearly different temporal patterns of GABA-A/BZ receptor subunit mRNA expression were observed: The expression of alpha3, alpha5, beta3 and gamma2 mRNAs was at a peak during perinatal development, followed by rapid downregulation thereafter. Conversely, alpha2, alpha4 and gamma1 mRNA expression was very low, or absent, during early development, and a pronounced increase was observed at the end of the first postnatal weeks Inferior olivary neurons are the primary source of climbing fibers innervating the Purkinje cells of the cerebellar cortex. The timecourse of afferent and efferent olivary connections precisely parallels the GABA-A/BZ receptor subunit changes in olivary neurons: During postnatal week two, olivary climbing fiber innervation of the target Purkinje cell regresses; the number of climbing fiber terminals innervating each Purkinje cell is reduced from greater than 3:1, as observed in neonates, to the 1:1 relationship observed in the adult cerebellar cortex. During the same period, olivary neurons become densely innervated by GABAergic afferents. This raises the possibility that the observed developmental switches in subunit expression may be related to epigenetic factors, such as a reduction in neurotrophic factors from the target Purkinje cell, or to stimulation by GABAergic cells of the deep cerebellar and other afferent nuclei. We will explore the role of a number of possible epigenetic mechanisms which may regulate GABA-A/BZ receptor subunit switching during development. These include the role of efferent and afferent connections, potential neurotrophic factors and increased electrical activity. In addition, the effect of subunit gene- deletion, and the generalizability of the subunit switching phenomenon will be studied.

该提案的目的是检查细胞相互作用 γ-氨基丁酸发育表达的潜在变化 酸性/苯二氮卓 (GABA-A/BZ) 受体亚基 mRNA 和配体结合 位于小鼠下橄榄核的位点。 GABA-A/BZ 受体是 被认为是由选定的α组成的五聚氯离子通道， beta、gamma、delta 和 rho 亚基，其中大多数有几个 同工型：α 1-6、β 1-4、γ 1-4 和 rho 1-2。我们已经证明， 哺乳动物中枢神经中存在的十三个亚基变体 系统中，alpha 2-5、beta 3、gamma 1-2 的表达显着 下橄榄核的水平。两个明显不同的时间 观察 GABA-A/BZ 受体亚基 mRNA 表达模式： α3、α5、β3 和 gamma2 mRNA 的表达在 围产期发育，随后迅速下调。 相反，α2、α4 和 gamma1 mRNA 表达量非常低，或者 在早期发育过程中不存在，并且观察到明显的增加 出生后第一周结束时，下橄榄神经元是 支配浦肯野细胞的攀爬纤维的主要来源 小脑皮质。橄榄传入和传出的时间进程 连接精确地平行于 GABA-A/BZ 受体亚基的变化 橄榄神经元：在出生后第二周，橄榄攀缘纤维 目标浦肯野细胞的神经支配退化；攀登次数 支配每个浦肯野细胞的纤维末端从更大 新生儿中观察到的 3:1 关系，与在新生儿中观察到的 1:1 关系相比 成人小脑皮质。在同一时期，橄榄神经元变成 由 GABA 能传入神经密集支配。这增加了可能性 观察到的亚基表达的发育开关可能是 与表观遗传因素有关，例如神经营养因子的减少 来自目标浦肯野细胞，或受到 GABA 能细胞的刺激 小脑深部和其他传入核团。我们将探讨一个角色的作用 许多可能调节 GABA-A/BZ 的表观遗传机制 发育过程中受体亚基的转换。这些角色包括 传出和传入连接、潜在的神经营养因子和 电活动增加。此外，亚基基因的作用- 删除，以及亚基转换现象的普遍性 将被研究。