A primo vascular system underneath the superior sagittal sinus in the brain of a rabbit.

The primo vascular systems (PVS) observed in the central nervous system have been limited to the ones floating in the cerebrospinal fluid. In those experiments, it was difficult to obtain the same results because the PVS was not fixed in a given anatomical position. In the current work, we report a finding of a PVS in a well-defined location, namely, underneath the superior sagittal sinus in the sagittal fissure, so that repetition of the experiments is possible. This provides a cornerstone for PVS research because the lack of reproducible sample-taking hindered a deeper study of the PVS, such as RNA sequencing or RNA microarray. This obstacle can be overcome through the discovery in the current work. This PVS showed characteristics of the PVS observed in other organs. It showed the bundle structure of subvessels, the parallel distributions of F-actins, and the rod-shaped nuclei. Furthermore, it had a primo node in front of the confluence of sinuses above the pineal body. It had branches shooting off from the main primo vessel in the subarachnoid space toward the cerebral hemispheres. The results indicate that this PVS underneath superior sagittal sinus has proper features to function as a flowing channel.