FIGURE 10.10. Independence of extracellular tortuosity and volume fraction during osmotic stress in rat neocortex in vitro.

FIGURE 10.10

Independence of extracellular tortuosity and volume fraction during osmotic stress in rat neocortex in vitro. Diffusion of TMA+ was measured using RTI; diffusion of fluorophore-labeled 3000 MW dextran was measured using IOI. Osmotic stress was induced by changing the NaCl content to alter osmolality of the bathing media for rat neocortical slices. Tortuosity measured with both molecules increases linearly as osmolality decreases below (i.e., becomes hypotonic) control value (305 mosmol kg−1), but the slope measured with the larger molecule (dextran) is greater than that measured with the smaller (TMA+). In hypertonic ACSF, the value of λ measured with both molecules quickly reaches a constant value, λ = 1.67 even though the osmolality of the medium continues to increase. In contrast to the behavior of λ, α varies smoothly and monotonically with osmolality, decreasing in hypotonic and increasing in hypertonic medium. (Reproduced from Kume-Kick, J., et al., J. Physiol., 542, 515–527, 2002.)

From: Chapter 10, Biophysical Properties of Brain Extracellular Space Explored with Ion-Selective Microelectrodes, Integrative Optical Imaging and Related Techniques

Cover of Electrochemical Methods for Neuroscience
Electrochemical Methods for Neuroscience.
Michael AC, Borland LM, editors.
Boca Raton (FL): CRC Press/Taylor & Francis; 2007.
Copyright © 2007, Taylor & Francis Group, LLC.

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