Rises in local neural activity trigger local increases of cerebral blood flow, which is essential to match local energy demands. However, the specific location of microvascular flow control is incompletely understood. Here, we used two-photon microscopy to observe brain microvasculature in vivo. Small spatial movement of a three-dimensional (3D) vasculature makes it challenging to precisely measure vessel diameter at a single x–y plane. To overcome this problem, we carried out four-dimensional (x–y–z–t) imaging of brain microvessels during exposure to vasoactive molecules in order to constrain the impact of brain movements on the recordings. We demonstrate that rises in synaptic activity, acetylcholine, nitric oxide, cyclic guanosine monophosphate, ATP-sensitive potassium channels, and endothelin-1 exert far greater effects on brain precapillary sphincters and first-order capillaries than on penetrating arterioles or downstream capillaries, but with similar kinetics. The high level of responsiveness at precapillary sphincters and first-order capillaries was matched by a higher level of α-smooth muscle actin in pericytes as compared to penetrating arterioles and downstream capillaries. Mathematical modeling based on 3D vasculature reconstruction showed that precapillary sphincters predominantly regulate capillary blood flow and pressure as compared to penetrating arterioles and downstream capillaries. Our results confirm a key role for precapillary sphincters and pericytes on first-order capillaries as sensors and effectors of endothelium- or brain-derived vascular signals.

局部神经活动的增加触发局部脑血流量增加，这对于匹配局部能量需求至关重要。然而，微血管流量控制的具体位置尚不完全清楚。在这里，我们使用双光子显微镜观察体内脑微血管系统。三维 (3D) 脉管系统的小空间运动使得在单个 x-y 平面上精确测量血管直径具有挑战性。为了克服这个问题，我们在暴露于血管活性分子期间对大脑微血管进行了四维 (x-y-z-t) 成像，以限制大脑运动对录音的影响。我们证明了突触活动、乙酰胆碱、一氧化氮、环磷酸鸟苷、ATP 敏感钾通道的增加，和内皮素-1 对脑毛细血管前括约肌和一级毛细血管的影响远大于对穿透小动脉或下游毛细血管的影响，但具有相似的动力学。与穿透性小动脉和下游毛细血管相比，毛细血管前括约肌和一级毛细血管的高水平反应与周细胞中更高水平的 α-平滑肌肌动蛋白相匹配。基于 3D 血管系统重建的数学模型表明，与穿透性小动脉和下游毛细血管相比，毛细血管前括约肌主要调节毛细血管血流量和压力。我们的结果证实了一级毛细血管上的毛细血管前括约肌和周细胞作为内皮或脑源性血管信号的传感器和效应器的关键作用。