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The vascular organ of lamina terminalis (VOLT), organum vasculosum of the lamina terminalis (OVLT), or supraoptic crest 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. It overlies the paraventricular nucleus of hypothalamus, and is involved in the secretion of vasopressin. The VOLT monitors the presence of peptides and macromolecules in the bloodstream, and conveys the information to the hypothalamus.

It is one of the three sensory circumventricular organs of the brain. The other four are secretory.

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). This region functions in the regulation of fluid and electrolyte balance by controlling thirst, sodium excretion, blood volume regulation, and vasopressin secretion.

Function

The VOLT is one of the three sensory circumventricular organs providing information to other brain regions.

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.

Neurons in the VOLT are osmoreceptors sensitive to the sodium content and osmotic pressure of blood. Neurons of the lamina terminalis project to the supraoptic nucleus and paraventricular nucleus to regulate the activity of vasopressin-secreting neurons. 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. These neurons also project to the median preoptic nucleus which is involved in controlling thirst.

References

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7. ^ Johnson, A. K (1985). "The periventricular anteroventral third ventricle (AV3V): Its relationship with the subfornical organ and neural systems involved in maintaining body fluid homeostasis". Brain Research Bulletin. 15 (6): 595–601. doi:10.1016/0361-9230(85)90209-6. PMID 3910170. S2CID 4781981.
8. Miyata, S (2015). "New aspects in fenestrated capillary and tissue dynamics in the sensory circumventricular organs of adult brains". Frontiers in Neuroscience. 9: 390. doi:10.3389/fnins.2015.00390. PMC 4621430. PMID 26578857.
9. ^ Johnson, A. K; Gross, P. M (1993). "Sensory circumventricular organs and brain homeostatic pathways". FASEB Journal. 7 (8): 678–86. doi:10.1096/fasebj.7.8.8500693. PMID 8500693. S2CID 13339562.
10. Fry, Mark; Ferguson, Alastair V. (July 2007). "The sensory circumventricular organs: Brain targets for circulating signals controlling ingestive behavior". Physiology & Behavior. 91 (4): 413–423. doi:10.1016/j.physbeh.2007.04.003. PMID 17531276.
11. ^ Gross, P. M; Weindl, A (1987). "Peering through the windows of the brain (review)". Journal of Cerebral Blood Flow & Metabolism. 7 (6): 663–72. doi:10.1038/jcbfm.1987.120. PMID 2891718. S2CID 18748366.
12. ^ McKinley, M. J; Allen, A. M; May, C. N; McAllen, R. M; Oldfield, B. J; Sly, D; Mendelsohn, F. A (2001). "Neural pathways from the lamina terminalis influencing cardiovascular and body fluid homeostasis". Clinical and Experimental Pharmacology and Physiology. 28 (12): 990–2. doi:10.1046/j.1440-1681.2001.03592.x. PMID 11903300. S2CID 43091000.
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• Ventricular system
• Neuroendocrinology