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Brief Dark Exposure Reduces Tonic Inhibition in Visual Cortex
Shiyong Huang1, Kristen Hokenson2, Sabita Bandyopadhyay3
1The Mind/Brain Institute, Johns Hopkins University, Baltimore, Maryland 21218, Program in Neuroscience, Hussman Institute for Autism, Baltimore, Maryland 21201.
Summary
Sensory experience, like dark exposure, reduces tonic inhibition in juvenile mouse visual cortex. This involves decreased delta subunit GABARs, potentially increasing neuronal firing.
Area of Science:
- Neuroscience
- Cellular Physiology
Background:
- Tonic inhibition, mediated by extrasynaptic GABA(A) receptors (GABARs), regulates neuronal excitability.
- This inhibition is influenced by factors like age, neurotransmitters, stroke, and epilepsy, but sensory experience's role is unexplored.
Purpose of the Study:
- To investigate the impact of sensory deprivation on tonic inhibition in the juvenile visual cortex.
- To determine if changes in GABAR subunit expression correlate with altered tonic inhibition.
Main Methods:
- Electrophysiological recordings in layer II/III pyramidal cells of juvenile mice (postnatal day 12-27).
- Assessment of tonic inhibitory conductance before and after a 2-day dark exposure period.
- Quantitative analysis of GABAR subunit levels, focusing on the delta subunit.
Main Results:
- A 2-day dark exposure significantly reduced tonic inhibitory conductance by approximately one-third in the visual cortex.
- This reduction was specifically linked to decreased levels of the delta subunit of GABARs.
- No significant changes in delta subunit levels were observed in the frontal cortex, indicating regional specificity.
Conclusions:
- Sensory experience, specifically visual deprivation, modulates tonic inhibition in the developing visual cortex.
- Reduced tonic inhibition, possibly via delta subunit downregulation, may represent a homeostatic mechanism to enhance neuronal activity in deprived circuits.
