Fig. 6

AQP1 and NKCC1 distribution in the CNS leptomeningeal vasculature. Scheme representing the mouse brain parenchyma, the skull and the meninges, which encompass the brain and also the spinal cord. The meninges are divided into the dura mater and the leptomeninges, corresponding to the arachnoid and pia mater. The brain and spinal parenchyma are separated from the meninges by the basal lamina and the glia limitans. The arachnoid mater forms the outer barrier of the CNS and underneath it lies the subarachnoid space (SAS), which is filled with CSF. Immune cells, namely macrophages and leucocytes, are sparsely present within the SAS, surveilling the healthy CNS. Additionally to its function as route for CSF and immune cells circulation, the SAS encloses the arterial blood supply to the CNS. Prior to entering the CNS parenchyma, leptomeningeal arteries branch and divide into arterioles. Within the parenchyma, penetrating arterioles and veins are tethered by astrocytes with highly polarized AQP4 distribution, a unique feature of the CNS vasculature. Schematic representation of cross sections of the leptomeningeal vasculature denotes AQP1 and NKCC1 expression by smooth muscle cells, which compose the tunica media of arterioles and veins. In contrast, endothelial cells within the tunica intima are devoid of both proteins. Notwithstanding, endothelial cells of capillaries and venules present both AQP1 and NKCC1