Both the SFO and OVLT are known circumventricular organs (CVOs) devoid of the normal blood brain barrier and have been shown to be directly responsive to actions of angiotensin II (AngII) [4, 5].
Oldfield, "Intravenous angiotensin II induces Fos-immunoreactivity in circumventricular organs of the lamina terminalis," Brain Research, vol.
Ciriello, "Effect of lesions of forebrain circumventricular organs
on c-fos expression in the central nervous system to plasma hypernatremia," Brain Research, vol.
In these circumventricular organs
(Figure 6-7), blood from the arteries supplying the brain enters capillary networks consisting of fenestrated capillaries and then returns to the venous circulation via the venous sinuses.
Aquaporin-4 is highly expressed in areas which either lack an endothelial blood-brain barrier (circumventricular organs)7 or where blood-brain barrier permeability is higher compared to other regions of the CNS, such as the optic nerve head.
Particular attention should be paid to lesions in circumventricular organs and the optic nerve head, since in both regions the blood-brain barrier is less tight than in other regions of the CNS, and AQP-4 is highly expressed at these sites.