Vascular organ of lamina terminalis
The vascular organ of lamina terminalis (VOLT) (also known as organum vasculosum of the lamina terminalis (OVLT), or supraoptic crest[1]) Is an ependymal[2] chemosensory organ[3] of the third ventricle situated beneath the lamina terminalis. It overlies the paraventricular nucleus of hypothalamus.[2] The VOLT monitors the presence of peptides and macromolecules in the bloodstream, and conveys the information to the hypothalamus.[3]
| Vascular organ of lamina terminalis | |
|---|---|
| Details | |
| Identifiers | |
| Latin | organum vasculosum laminae terminalis |
| MeSH | D066278 |
| NeuroNames | 383 |
| NeuroLex ID | nlx_anat_100313 |
| TA98 | A14.1.08.940 |
| TA2 | 5781 |
| FMA | 62315 |
| Anatomical terms of neuroanatomy | |
It is one of the four sensory circumventricular organs of the brain (the others being the subfornical organ, the median eminence, and the area postrema).[4]
Anteroventral third ventricle region
The VOLT, median eminence, and subfornical organ are interconnected with the mid-ventral hypothalamus, and together these three structures surround the third ventricle, a complex often called the anteroventral region of the third ventricle ("AV3V" region).[4][5][6] This region functions in the regulation of fluid and electrolyte balance by controlling thirst, sodium excretion, blood volume regulation, and vasopressin secretion.[5][7]
Function
The VOLT is one of the four sensory circumventricular organs providing information to other brain regions (others are median eminence, subfornical organ, and area postrema).[4][8][9]
VOLT capillaries do not have a blood–brain barrier, and so neurons in this region can respond to circulating factors present in the systemic circulation.[4][7]
Neurons in the VOLT are osmoreceptors sensitive to the sodium content and osmotic pressure of blood.[5] Neurons of the lamina terminalis project to the supraoptic nucleus and paraventricular nucleus to regulate the activity of vasopressin-secreting neurons.[7] In a situation of lowered blood volume, secretion of renin by the kidneys results in the production of angiotensin II, which stimulates receptors in the VOLT and subfornical organ to complete a positive feedback loop.[7][10][11] These neurons also project to the median preoptic nucleus which is involved in controlling thirst.[4][7][10]