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Int J Mol Sci. 2017 Aug 18;18(8). pii: E1798. doi: 10.3390/ijms18081798.

Aquaporin-4 Functionality and Virchow-Robin Space Water Dynamics: Physiological Model for Neurovascular Coupling and Glymphatic Flow.

Author information

1
Center for Integrated Human Brain Science, Brain Research Institute, University of Niigata, Niigata 951-8585, Japan. ttnakada@ucdavis.edu.
2
Department of Neurology, University of California, Davis, VANCHCS, Martinez, CA 94553, USA. ttnakada@ucdavis.edu.
3
Center for Integrated Human Brain Science, Brain Research Institute, University of Niigata, Niigata 951-8585, Japan. ilkwee@ucdavis.edu.
4
Department of Neurology, University of California, Davis, VANCHCS, Martinez, CA 94553, USA. ilkwee@ucdavis.edu.
5
Center for Integrated Human Brain Science, Brain Research Institute, University of Niigata, Niigata 951-8585, Japan. higara@bri.niigata-u.ac.jp.
6
Center for Integrated Human Brain Science, Brain Research Institute, University of Niigata, Niigata 951-8585, Japan. yuji-s@bri.niigata-u.ac.jp.

Abstract

The unique properties of brain capillary endothelium, critical in maintaining the blood-brain barrier (BBB) and restricting water permeability across the BBB, have important consequences on fluid hydrodynamics inside the BBB hereto inadequately recognized. Recent studies indicate that the mechanisms underlying brain water dynamics are distinct from systemic tissue water dynamics. Hydrostatic pressure created by the systolic force of the heart, essential for interstitial circulation and lymphatic flow in systemic circulation, is effectively impeded from propagating into the interstitial fluid inside the BBB by the tightly sealed endothelium of brain capillaries. Instead, fluid dynamics inside the BBB is realized by aquaporin-4 (AQP-4), the water channel that connects astrocyte cytoplasm and extracellular (interstitial) fluid. Brain interstitial fluid dynamics, and therefore AQP-4, are now recognized as essential for two unique functions, namely, neurovascular coupling and glymphatic flow, the brain equivalent of systemic lymphatics.

KEYWORDS:

Hagen-Poiseuille equation; glia limitans externa; interstitial flow; rCBF; starling resister

PMID:
28820467
PMCID:
PMC5578185
DOI:
10.3390/ijms18081798
[Indexed for MEDLINE]
Free PMC Article

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