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The vascular organ of lamina terminalis (VOLT), organum vasculosum of the lamina terminalis (OVLT), or supraoptic crest[1] is a sensory organ, one of the circumventricular organs of the third ventricle within the lamina terminalis. It is covered with pia mater, and lined with ependyma.[2][3] It overlies the paraventricular nucleus of hypothalamus,[4] and is involved in the secretion of vasopressin.[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 three sensory circumventricular organs of the brain.[5] The other four are secretory.[6]
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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).[7][8] This region functions in the regulation of fluid and electrolyte balance by controlling thirst, sodium excretion, blood volume regulation, and vasopressin secretion.[7][9]
The VOLT is one of the three sensory circumventricular organs providing information to other brain regions.[6][10]
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.[11][9]
Neurons in the VOLT are osmoreceptors sensitive to the sodium content and osmotic pressure of blood.[7] Neurons of the lamina terminalis project to the supraoptic nucleus and paraventricular nucleus to regulate the activity of vasopressin-secreting neurons.[9] 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.[9][12][13] These neurons also project to the median preoptic nucleus which is involved in controlling thirst.[11][9][12]
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