To our own surprise, we discovered a new vascular portal pathway linking the suprachiasmatic nucleus (SCN) to the organum vasculosum of the lamina terminalis (OVLT). The OVLT has long been considered a “window to the brain” as it has leaky blood vessels, lacks a BBB, communicates with both the CSF and interstitial fluids (ISF), and has large perivascular spaces (PVSs). The “glymphatic hypothesis” has brought to renewed attention the importance of sleep and PVSs in clearing of brain waste. It has also reawakened interest in how the circadian timing system to contributes to the functions of sleep. The identification of the SCN-OVLT vascular and perivascular pathway points to a mechanism whereby the SCN’s diffusible output signals can be relayed and amplified to impact the entire brain and body and how the circadian contribution to sleep regulation. To start the study of function, our laboratory has focused on vasopressin, a key diffusible output of the SCN circadian clock, as this provides an entry point for examining how vascular and perivascular fluids can influence global regulation of sleep–wake cycles. The existence of numerous vascular portal pathways and their large PVSs opens unprecedented opportunities to explore new routes for inputs to and outputs from the SCN and more generally, how information from the connectome, angiome and “perivasculome” are integrated.

More information:

• https://psychology.columbia.edu/content/rae-silver