IMPERMEANT ANIONS ARE INVOLVED IN SETTING THE NEURONAL CHLORIDE CONCENTRATION, IMPLICATIONS FOR SEIZURE TREATMENT
Abstract number :
1.021
Submission category :
1. Translational Research: 1A. Mechanisms
Year :
2014
Submission ID :
1867726
Source :
www.aesnet.org
Presentation date :
12/6/2014 12:00:00 AM
Published date :
Sep 29, 2014, 05:33 AM
Authors :
Joseph Glykys, Volodymyr Dzhala, Kiyoshi Egawa, Trevor Balena, Yero Saponjian, Kishore Kuchibhotla, Brian Bacskai, Krishtopher Kahle, Thomas Zeuthen and Kevin Staley
Rationale: Neuronal chloride concentration [Cl-]i is an important determinant of GABAA receptor (GABAAR)-mediated inhibition and cytoplasmic volume regulation. Equilibrative cation-chloride cotransporters (CCC) move Cl- across the membrane. However, new evidence suggests CCCs are not the sole determinant of [Cl-]i. Methods: We tested the effects of specific NKCC1 and KCC2 blockade, osmotic challenge by mannitol, extracellular matrix disruption and cytotoxic alteration of volume constraints, induced by seizures, on neuronal [Cl-]i using two-photon imaging of brain slices from Clomeleon mice (genetically encoded ratiometric fluorophore sensitive to changes in [Cl-]i). Results: Our results demonstrated that cytoplasmic impermeant anions ([A]i) and polyanionic extracellular matrix glycoproteins ([A]o) constrain the local neuronal [Cl-]. In healthy neurons, CCC inhibition had modest effects on [Cl-]i and neuronal volume, but substantial changes were produced by alterations of the balance between [A]i and [A]o. During seizures, there was a correlated increase of [Cl-]i and neuronal volume Conclusions: In physiological conditions, CCC are important elements of Cl- homeostasis, but local impermeant anions determine the homeostatic set-point for [Cl-], and hence, neuronal volume and the polarity of local GABAAR signaling. Pathological conditions that alter [A], like traumatic brain injury, will lead to changes in [Cl-]i and may require different therapeutic approaches for seizure treatment.
Translational Research