First map of intracellular chloride in neurons in vivo

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The chloride and the intracellular pH regulation plays a key role in many neural functions. Changes in chloride levels could regulate the mechanisms of complex pathologies such as autism or epilepsy. A recent study, carried out thanks to the collaboration of several researchers of NEST, the Istituto Nanoscienze of CNR and Scuola Normale Superiore, and of the IIT of Genoa, the CNR of Trento and the University of Helsinki, shows new and fascinating results obtained through an innovative technique. This methodology allows mapping, in vivo, for the first time, of the chloride ions and the pH concentration (level of acidity) at an intracellular level in the pyramidal neurons of the central nervous system.

 

Fig. 1 Panel A – pH and chloride mapping in vivo (MM are millimoles) for a 5-day life mouse. Panel B – Same process for a mouse of 32 days of life. Panel C – Intracellular pH for three different stages of development of mice. Panel D – Intracellular chloride for three different stages of development of mice. You can see the decrease in concentration as the age increases.

This technique uses a new “sensor”, LSSmClopHensor, formed by the merge of the green fluorescent protein, E2GFP with a red fluorescent protein, LSSmKate2. The measurements with ClopHensor were performed in vivo in the brain of anesthetized mice by imaging with two photons microscopy.

This study shows principally that chloride changes during development, whereas pH does not vary. Therefore, we can notice in the figure here reproduced that the chloride concentration decreases progressively from P4-5 (postnatal day 4-5) to P8-10 and up to P18-51, i.e. in the adult mouse, where it reaches values less than 20 millimoles [mM] (as shown in panel D of Fig. 1, the peak shifts to the left). However, the intracellular pH remains substantially unchanged (panel C of Fig. 1).

This methodology opens up new opportunities for the study of the central nervous system’s development mechanisms and its related pathologies, including autism and epilepsy.

Translated from Italian by Cristina Trocin

Author: Marcos Valdes

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