The essential function of the circulatory system is to continuously and efficiently supply the O₂ and nutrients necessary to meet the metabolic demands of every cell in the body, a function in which vast capillary networks play a key role. Capillary networks serve an additional important function in the central nervous system: acting as a sensory network, they detect neuronal activity in the form of elevated extracellular K⁺ and initiate a retrograde, propagating, hyperpolarizing signal that dilates upstream arterioles to rapidly increase local blood flow. Yet, little is known about how blood entering this network is distributed on a branch-to-branch basis to reach specific neurons in need. Here, we demonstrate that capillary-enwrapping projections of junctional, contractile pericytes within a postarteriole transitional region differentially constrict to structurally and dynamically determine the morphology of capillary junctions and thereby regulate branch-specific blood flow. We further found that these contractile pericytes are capable of receiving propagating K⁺-induced hyperpolarizing signals propagating through the capillary network and dynamically channeling red blood cells toward the initiating signal. By controlling blood flow at junctions, contractile pericytes within a functionally distinct postarteriole transitional region maintain the efficiency and effectiveness of the capillary network, enabling optimal perfusion of the brain.

循环系统的基本功能是连续有效地供应O ₂和满足人体每个细胞代谢需求所需的营养素，其中巨大的毛细血管网起着关键作用。毛细血管网络在中枢神经系统中起着另外一个重要功能：作为感觉网络，它们以升高的细胞外K ⁺的形式检测神经元活动。并发出逆行，传播，超极化信号，使上游小动脉扩张，从而迅速增加局部血流量。然而，对于进入该网络的血液如何以分支到分支的方式分布以到达需要的特定神经元知之甚少。在这里，我们证明了在小动脉后过渡区域内的交界，收缩性周细胞的毛细管包裹投影不同地收缩，从而在结构上和动态地确定了毛细管接头的形态，从而调节了分支特定的血流。我们进一步发现这些可收缩的周细胞能够接受繁殖的K ⁺诱导的超极化信号通过毛细血管网络传播，并朝着起始信号动态引导红细胞。通过控制连接处的血流，功能不同的小动脉后过渡区域内的收缩性周细胞可保持毛细管网络的效率和有效性，从而实现大脑的最佳灌注。