VOL. 1, No. 2 / 3, July 2004

B. Vigh, et al. [2004] Med Hypotheses Res 1: 77-100.

The Circumventricular Organs of the Brain: Do They
Represent a Cerebrospinal fluid-Dependent
Regulatory System?

B. Vigh*, M.J. Manzano e Silva, C.L. Frank, C. David, S.J. Czirok,
C. Vincze, G. Racz, A. Lukats and A. Szel

Department of Human Morphology and Developmental Biology, Semmelweis University,
Budapest, Hungary

Abstract.  The circumventricular organs are specially organized areas in the wall of
the brain ventricles. The close contact of their cells to the internal and external
cerebrospinal fluid (CSF) spaces supports the hypothesis that their function is connected
to the maintenance of the homeostasis of these fluids. The neurons of the subfornical
organ, and area postrema send receptor dendrites to the perivascular surface of the
nervous tissue and may perceive the composition of the perivasal fluid. Some of the
circumventricular organs form neurohormonal release areas similar to those of the
neurohypophysis, the lack of blood-brain barrier in these areas primarily serves the
hormone release. The CSF-contacting neurons of the paraventricular organ form dendritic
terminals in the third ventricle and are supposed to be chemoreceptors. Similar neurons in
the lateral septal organ and preoptic recess of submammalians contain opsins and
represent the deep brain photoreceptors detecting the illumination of the CSF and
influence photoperiodicity. CSF-contacting neurons around the central canal show
cytologic similarity to known mechanoreceptors and are supposed to perceive the flow or
pressure of the CSF. Neurons sending a sensory cilium into the intercellular space may
perceive the chemical composition of the intercellular fluid that is important in the
metabolism and non-synaptic signal transmission of the brain. The subcommisural organ
contains special ependymal cells secreting the Reissner's fiber which extends into the
mesencephalic aqueduct, fourth ventricle and central canal. The fiber may help the
supposed mechanoreceptive task of the spinal CSF-contacting neurons and seems to be
involved in the pathogenesis of hydrocephalus.

*Address all correspondence to: Dr. B. Vígh, Department of Human Morphology and
Developmental Biology, Semmelweis University, Tüzoltó u. 58. H-1094, Budapest,
Hungary.  FAX: 36-1-215-3064. E-mail:

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