Corpus: Vascular organ of lamina terminalis

The vascular organ of lamina terminalis, or VOLT for short, is a rudimentary vascular loop located in the lamina terminalis of the third ventricle of the brain. It has a fenestrated endothelium and is classified as a circumventricular organ.

The VOLT is situated at the rostral end of the third ventricle. It is divided into two anatomically and functionally distinct areas: the inner capillary plexus and the outer lateral zone. It contains neurons and glial cells.

Small molecules in the bloodstream enter the capillary plexus and then diffuse sequentially into the lateral zone. This zone integrates the information and transmits it to downstream regions, such as the hypothalamus.

The cells of the VOLT contain receptors for insulin, leptin, endothelin, and vasopressin, among others, allowing them to monitor the body's metabolic status. The VOLT also houses specialized osmoreceptors that respond sensitively to the sodium content and osmotic pressure of the blood. These sensory cells, along with the subfornical organ, are stimulated by angiotensin II during hypovolemia. They project into the paraventricular nucleus and supraoptic nucleus, contributing to the sensation of thirst.

• Jeong et al Sensory Circumventricular Organs, Neuroendocrine Control, and Metabolic Regulation Metabolites 2021