Figure 4.

ISF drainage routes in normal rats and demyelinated rats. Due to the obstruction of the compact myelinated fibre tracts (yellow frame and yellow arrow), the traced ISF from the caudate nucleus (Cn)(pink arrow) could not drain to the ECS of the thalamus (Tha) and vice versa, even though these two regions are adjacent to one another. Myelin is identified as the transportation barrier to ISF drainage in the deep brain. At the meantime, it guides the ISF in the caudate nucleus draining to ipsilateral cortex and finally into the subarachnoid space, which maintains the pathway of ISF-CSF exchange. When the integrity of myelin is interrupted (white frame and white arrow), abnormal communication of ISF from the two regions emerges which indicates that the ISF from caudate nucleus (pink arrow) could be drained into the adjacent thalamus (red arrow) and less ISF from caudate nucleus could be drained to the cortex regions. Then the local homeostasis was interrupted. This is a schematic figure for identification purpose and is not be scale.