Pappas Anthony C, Koide Masayo, Wellman George C
Department of Pharmacology, University of Vermont, Burlington, VT, USA.
Department of Pharmacology, University of Vermont, Burlington, VT, USA
J Cereb Blood Flow Metab. 2016 Nov;36(11):1901-1912. doi: 10.1177/0271678X16650911. Epub 2016 May 20.
Neurovascular coupling supports brain metabolism by matching focal increases in neuronal activity with local arteriolar dilation. Previously, we demonstrated that an emergence of spontaneous endfoot high-amplitude Ca signals (eHACSs) caused a pathologic shift in neurovascular coupling from vasodilation to vasoconstriction in brain slices obtained from subarachnoid hemorrhage model animals. Extracellular purine nucleotides (e.g., ATP) can trigger astrocyte Ca oscillations and may be elevated following subarachnoid hemorrhage. Here, the role of purinergic signaling in subarachnoid hemorrhage-induced eHACSs and inversion of neurovascular coupling was examined by imaging parenchymal arteriolar diameter and astrocyte Ca signals in rat brain slices using two-photon fluorescent and infrared-differential interference contrast microscopy. We report that broad-spectrum inhibition of purinergic (P2) receptors using suramin blocked eHACSs and restored vasodilatory neurovascular coupling after subarachnoid hemorrhage. Importantly, eHACSs were also abolished using a cocktail of inhibitors targeting G-coupled P2Y receptors. Further, activation of P2Y receptors in brain slices from un-operated animals triggered high-amplitude Ca events resembling eHACSs and disrupted neurovascular coupling. Neither tetrodotoxin nor bafilomycin A1 affected eHACSs suggesting that purine nucleotides are not released by ongoing neurotransmission and/or vesicular release after subarachnoid hemorrhage. These results indicate that purinergic signaling via P2Y receptors contributes to subarachnoid hemorrhage-induced eHACSs and inversion of neurovascular coupling.
神经血管耦合通过使神经元活动的局部增加与局部小动脉扩张相匹配来支持脑代谢。此前，我们证明，自发性终足高幅度钙信号（eHACSs）的出现导致了从蛛网膜下腔出血模型动物获得的脑片中神经血管耦合从血管舒张向血管收缩的病理性转变。细胞外嘌呤核苷酸（如ATP）可触发星形胶质细胞的钙振荡，并且在蛛网膜下腔出血后可能会升高。在此，通过使用双光子荧光显微镜和红外微分干涉对比显微镜对大鼠脑片实质小动脉直径和星形胶质细胞钙信号进行成像，研究了嘌呤能信号在蛛网膜下腔出血诱导的eHACSs和神经血管耦合反转中的作用。我们报告称，使用苏拉明对嘌呤能（P2）受体进行广谱抑制可阻断eHACSs，并在蛛网膜下腔出血后恢复血管舒张性神经血管耦合。重要的是，使用靶向G偶联P2Y受体的抑制剂混合物也消除了eHACSs。此外，在未手术动物的脑片中激活P2Y受体可引发类似于eHACSs的高幅度钙事件，并破坏神经血管耦合。河豚毒素和巴弗洛霉素A1均未影响eHACSs，这表明嘌呤核苷酸在蛛网膜下腔出血后不是通过持续的神经传递和/或囊泡释放来释放的。这些结果表明，通过P2Y受体的嘌呤能信号传导促成了蛛网膜下腔出血诱导的eHACSs和神经血管耦合的反转。
