Cerebrospinal Fluid Secretion by the Choroid Plexus

Abstract

The choroid plexus epithelium is a cuboidal cell monolayer, which produces the majority of the cerebrospinal fluid. The concerted action of a variety of integral membrane proteins mediates the transepithelial movement of solutes and water across the epithelium. Secretion by the choroid plexus is characterized by an extremely high rate and by the unusual cellular polarization of well-known epithelial transport proteins. This review focuses on the specific ion and water transport by the choroid plexus cells, and then attempts to integrate the action of specific transport proteins to formulate a model of cerebrospinal fluid secretion. Significant emphasis is placed on the concept of isotonic fluid transport across epithelia, as there is still surprisingly little consensus on the basic biophysics of this phenomenon. The role of the choroid plexus in the regulation of fluid and electrolyte balance in the central nervous system is discussed, and choroid plexus dysfunctions are described in a very diverse set of clinical conditions such as aging, Alzheimer's disease, brain edema, neoplasms, and hydrocephalus. Although the choroid plexus may only have an indirect influence on the pathogenesis of these conditions, the ability to modify epithelial function may be an important component of future therapies.

Acid–base physiology, neurobiology and behaviour in relation to CO2-induced ocean acidification

“…3, Table 3). This is an important point, because CSF and BIF have different ionic and A-B composition compared with blood plasma (reviewed in Damkier et al, 2013;Syková and Nicholson, 2008), neurons have different composition compared with whole brain homogenate, and the Goldman equation is extremely sensitive to even minute differences in the parameters used. In fact, a tiny difference in one of the parameters can change the calculation of GABA A R equilibrium potential from hyperpolarizing to depolarizing in relation to V m , and minute differences in various parameters can compensate for (or potentiate) each other's effects on equilibrium potential (see Basic neurobiology considerations).…”

“…Furthermore, at least in humans, the brain is composed of similar numbers of neurons and glial cells (Azevedo et al, 2009), so measurements on brain homogenates provide an average estimation of the two (plus contaminating CSF and BIF). Additionally, the choroid plexus, blood-brain barrier (see Glossary) and astrocytes tightly regulate the ionic and A-B composition of CSF and BIF (reviewed in Damkier et al, 2013;Syková and Nicholson, 2008). In fact, the chief evolutionary selective pressure favouring the evolution of the blood-brain barrier is believed to be the maintenance of a stable ionic environment to promote neuronal function (Abbott, 1992;Cserr and Bundgaard, 1984).…”

The relevance of α-KLOTHO to the central nervous system: Some key questions

“…The choroid plexus has three roles: i) a barrier between blood and cerebrospinal fluid (CSF); ii) the major source of CSF production; and iii) a source of secreted soluble factors for the CSF (Damkier et al, 2013). Since soluble α-Klotho protein is detectable in CSF, it is reasonable to assume this protein has been produced by the choroid plexus.…”

Alzheimer’s Disease Pathogenesis: The Denied Access Model

“…Bulk flow through the ECS remains a debated issue [81]. Flow typically occurs via osmotically balanced fluid secretion across the BBB but can also be generated as fluid secretion from cells [82] and the choroid plexuses [83]. One research group determined bulk flow only occurs in perivascular spaces surrounding capillaries and little to no flow occurs throughout the remaining ECS [84].…”