Developmental Decrease of Neuronal Chloride Concentration Is Independent of Trauma in Thalamocortical Brain Slices.

Area of Science:

• Neuroscience
• Cellular Neuroscience
• Developmental Neuroscience

Background:

• Intraneuronal chloride concentration ([Cl-]i) is critical for GABAA synapse signaling polarity in the central nervous system.
• Hippocampal slice preparation increases [Cl-]i in superficial layers, but effects on neocortex and thalamus, and developmental changes, remain unclear.

Purpose of the Study:

• To investigate the impact of slicing trauma on intraneuronal chloride concentration ([Cl-]i) in neocortical and thalamic slices.
• To examine developmental changes in [Cl-]i in these brain regions from post-natal day 5 (P5) to P20.

Main Methods:

• Utilized chloride imaging (Cl- imaging) in acute thalamocortical brain slices from mice.
• Analyzed [Cl-]i in relation to distance from the cut surface across different developmental ages (P5-P20).

Main Results:

• Intraneuronal chloride concentration ([Cl-]i) was elevated in the superficial layers of both neocortical and thalamic slices at all developmental ages studied.
• A developmental decrease in [Cl-]i was observed, independent of the acute trauma from slicing.
• Neurons nearest to the slicing trauma consistently showed elevated [Cl-]i across all ages and brain regions.

Conclusions:

• Intraneuronal chloride concentration ([Cl-]i) undergoes developmental progression in the neocortex and thalamus between P5 and P20.
• Acute trauma from brain slicing elevates [Cl-]i in superficial neurons of the neocortex and thalamus throughout development.
• These findings highlight the influence of both developmental stage and experimental manipulation on neuronal chloride homeostasis.