Astrocytes and neurovascular coupling

描述（由申请人提供）：脑血流与局部神经元需求相耦合。然而，如果上游动脉小动脉不扩张，使更多的血液到达扩张的下游血管，这种耦合就会受到损害。起源于神经元的血管舒张信号到达由胶质细胞限制（GL）从实质神经元分离出来的枢轴小动脉的过程尚不清楚。中心假设是，所涉及的信号机制将随着神经元激活强度的增加而变化。为此，我们将比较在多种药物和分子干预的情况下，癫痫发作（局部双颊碱）和坐骨神经刺激（SNS）时枕小动脉的反应。以下具体假设将被验证：1)神经元激活通过涉及星形胶质细胞（和GL）和血管内皮的信号传导过程诱导心肌动脉扩张（PAD）。这些研究将使用经过验证的GL或内皮选择性损伤模型。2)神经元激活诱导的PAD涉及星形细胞网络、间隙连接和/或半通道内ATP外排相关信号的传播。药物阻断和sirna连锁敲低都将用于靶向特定的ATP受体和连接蛋白43。3)由GL引起的旁分泌因子作用于头血管引起松弛。主要的候选物质是K+和ATP水解（腺苷；ADP）的分解产物，通过外核苷酶（EN）作用形成。将测试特异性药物阻滞剂或sirna连接的K+释放通道（BKCa和kir4.1）和ENs对癫痫发作与sns诱导的PAD的影响。4)释放的K+和腺苷分别刺激基底动脉平滑肌上的kir2.1通道和腺苷A2A受体，可能是相互作用的。如上所述，将应用特定的药物和基于sirna的干预措施。这一结果将为研究神经元在活动增强期间如何向特定的脑血管发出扩张信号提供重要的新见解。由此产生的营养物质输送到激活神经元的增加，确保了正常的大脑功能，并在病理状态下提供了保护。源自神经元的血管舒张信号如何到达动脉小动脉仍不清楚。这个项目的核心目标是确定通过增加的神经元活动信号动脉扩张的机制。中心假设是星形胶质细胞和胶质细胞界限代表了由神经激活引起的枢轴小动脉扩张的重要信号通道。

DESCRIPTION (provided by applicant): Cerebral blood flow is coupled to local neuronal demands. However, this coupling would be compromised without upstream dilation in pial arterioles to permit more blood to reach dilated downstream vessels. The process that permits vasodilating signals, originating in neurons, to reach the pial arterioles, which are isolated from parenchymal neurons by the glia limitans (GL), is unclear. The central hypothesis is that the signaling mechanisms involved will vary as the intensity of the neuronal activation increases. To that end, we will compare pial arteriolar responses during seizure (topical bicuculline) and sciatic nerve stimulation (SNS) in the presence of a variety of pharmacologic and molecular interventions. The following specific hypotheses will be tested: 1) Neuronal activation induces pial arteriolar dilation (PAD) via a signaling process involving astrocytes (and the GL) and vascular endothelium. These studies will use validated models for selective injury to the GL or endothelium. 2) Neuronal activation-induced PAD involves ATP efflux-related signal propagation within astrocytic networks and gap junctions and/or hemichannels. Both pharmacologic blockade and siRNA-linked knockdown will be used to target specific ATP receptors and connexin-43. 3) Paracrine factors arising from the GL act on pial vessels to elicit relaxation. The leading candidates are K+ AND breakdown products of ATP hydrolysis (adenosine; ADP), formed via ectonucleotidase (EN) action. The effects of specific pharmacologic blockers or siRNA-linked knockdown of K+ release channels (BKCa and Kir-4.1) and ENs, on seizure- vs SNS-induced PAD will be tested. 4) The released K+ and adenosine, respectively, stimulate Kir-2.1 channels and adenosine A2A receptors, perhaps interactively, on pial arteriolar smooth muscle. As above, specific pharmacologic and siRNA-based interventions will be applied. The results will provide vital new insights into how neurons, during periods of enhanced activity, signal specific cerebral vessels to dilate. The resulting increase in nutrient delivery to activated neurons acts to ensure normal brain function and provides protection in pathologic states. How vasodilating signals, originating in the neurons, reach the pial arterioles remain unclear. The core objective of this project is to identify mechanisms through which increased neuronal activity signals pial arterioles to dilate. The central hypothesis is that astrocytes and the glia limitans represent a vital signaling conduit in the pial arteriolar dilation arising from neural activation.