A fundamental property of animal cells is their ability to maintain a constant volume throughout life. In neurons, the possibility of changes in ionic composition and hence in cell volume is present at all times. This is a consequence of their small volume/surface ratio in conjunction with their synaptic and all-or-none electrical activity. Under physiologic conditions neurons are able to maintain and restore the ionic gradients which determine their resting membrane potential and osmotic balance. In spite of their importance, little is known about the mechanisms underlying cell volume regulation (CVR) and cell volume maintenance (CVM) in neurons. Furthermore, nerve cell swelling (cytotoxic edema), a dreaded complication of ischemia or trauma, has been postulated to result from loss of control of cell volume. Clearly further advances in pathophysiology of brain edema will require elucidation of the membrane mechanisms underlying CVR and CVM as well as the factors eliciting nerve cell swelling. This is a proposal to study the basic membrane mechanisms with which neurons are .equipped to regulate and maintain their volume in isosmotic and anisosmotic media.
We aim to ascertain how nerve cells respond to hyposmotic and hyperosmotic challenges , whether they are endowed with mechanisms for regulatory volume adjustments, and what is the nature of these mechanisms. In isosmotic media we want to know: a) the role played by the Na+/K4+ pump in CVM, and the mechanism involved in volume regulation when the pump is inhibited; b) the role of anion transport in CVM; and c) whether cell volume can be altered by firing activity and how nerve cells restore their volume under these conditions. These studies will be conducted on identified land snail neurons and frog dorsal root ganglion cells. These cell types are chosen because: i) they are relatively large; ii) their cell bodies are nearly spherical; iii) many of their membrane carriers and channels have been characterized; iv) their intracellular ionic activities are known; v) they can be easily isolated and maintained in vitro for optical measurements; vi) they are examples of an invertebrate and a vertebrate neuron. Cell volume changes and membrane voltage will be measured with microelectrodes, using intracellular TMA+ as a volume marker. Intracellular ion -activities will be measured with ion-selective microelectrodes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS029227-03
Application #
2267465
Study Section
Neurological Sciences Subcommittee 1 (NLS)
Project Start
1991-04-01
Project End
1995-03-31
Budget Start
1993-04-01
Budget End
1995-03-31
Support Year
3
Fiscal Year
1993
Total Cost
Indirect Cost
Name
University of Texas Medical Br Galveston
Department
Physiology
Type
Schools of Medicine
DUNS #
041367053
City
Galveston
State
TX
Country
United States
Zip Code
77555
Blanco, Víctor M; Márquez, Martín S; Alvarez-Leefmans, Francisco J (2013) Parallel changes in intracellular water volume and pH induced by NH(3)/NH(4)(+) exposure in single neuroblastoma cells. Cell Physiol Biochem 32:57-76
Mao, Shihong; Garzon-Muvdi, Tomas; Di Fulvio, Mauricio et al. (2012) Molecular and functional expression of cation-chloride cotransporters in dorsal root ganglion neurons during postnatal maturation. J Neurophysiol 108:834-52
Rocha-Gonzalez, Hector I; Mao, Shihong; Alvarez-Leefmans, Francisco J (2008) Na+,K+,2Cl- cotransport and intracellular chloride regulation in rat primary sensory neurons: thermodynamic and kinetic aspects. J Neurophysiol 100:169-84
Ares, Gustavo R; Caceres, Paulo; Alvarez-Leefmans, Francisco J et al. (2008) cGMP decreases surface NKCC2 levels in the thick ascending limb: role of phosphodiesterase 2 (PDE2). Am J Physiol Renal Physiol 295:F877-87
Munoz, Alberto; Mendez, Pablo; DeFelipe, Javier et al. (2007) Cation-chloride cotransporters and GABA-ergic innervation in the human epileptic hippocampus. Epilepsia 48:663-73
Alvarez-Leefmans, Francisco J; Herrera-Perez, Jose J; Marquez, Martin S et al. (2006) Simultaneous measurement of water volume and pH in single cells using BCECF and fluorescence imaging microscopy. Biophys J 90:608-18
Granados-Soto, Vinicio; Arguelles, Carlos F; Alvarez-Leefmans, Francisco J (2005) Peripheral and central antinociceptive action of Na+-K+-2Cl- cotransporter blockers on formalin-induced nociception in rats. Pain 114:231-8
Hamann, Steffen; Herrera-Perez, Jose Jaime; Bundgaard, Magnus et al. (2005) Water permeability of Na+-K+-2Cl- cotransporters in mammalian epithelial cells. J Physiol 568:123-35
Marty, Serge; Wehrle, Rosine; Alvarez-Leefmans, Francisco Javier et al. (2002) Postnatal maturation of Na+, K+, 2Cl- cotransporter expression and inhibitory synaptogenesis in the rat hippocampus: an immunocytochemical analysis. Eur J Neurosci 15:233-45
Alvarez-Leefmans, F J; Leon-Olea, M; Mendoza-Sotelo, J et al. (2001) Immunolocalization of the Na(+)-K(+)-2Cl(-) cotransporter in peripheral nervous tissue of vertebrates. Neuroscience 104:569-82

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