Subfornical organ

Subfornical organ
Mesial aspect of a brain sectioned in the median sagittal plane. (Subfornical organ not labeled, but fornix and foramen of Monro are both labeled near the center.)
Details
Identifiers
Latin	organum subfornicale
MeSH	A08.713.840
NeuroNames	hier-437
NeuroLex ID	Subfornical organ
Dorlands /Elsevier	o_06/12596286
TA	A14.1.08.412 A14.1.09.449
FMA	75260
Anatomical terms of neuroanatomy []

The subfornical organ (SFO), situated on the ventral surface of the fornix (the reasoning behind the organ's name), at the interventricular foramina (foramina of Monro), is one of the circumventricular organs of the brain, meaning that it is highly vascularized and does not have a blood-brain barrier, unlike the vast majority of regions in the brain. The SFO is a sensory circumventricular organ responsive to a wide variety of hormones and neurotransmitters, as opposed to a secretory circumventricular organ.

Similar to the organum vasculosum of the lamina terminalis (OVLT), the subfornical organ is a sensory circumventricular organ situated in the lamina terminalis and lacking the blood-brain barrier, the absence of which characterizes the circumventricular organs. Protruding into the third ventricle of the brain, the SFO can be divided into six anatomical zones based on its capillary topography: two zones in the coronal plane and four zones in the sagittal plane. The central zone is composed of the glial cells, neuronal cell bodies and high density of fenestrated capillaries. Conversely, the rostral and caudal areas have lower capillary density and are mostly made of nerve fibers with fewer neurons and glial cells seen in this area. Functionally, however, the SFO may be viewed in two portions, the dorsolateral peripheral division and the ventromedial core segment.

The subfornical organ also contains endothelin receptors mediating vasoconstriction and high rates of glucose metabolism mediated by calcium channels.