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Subtype-selective Electroporation of Cortical Interneurons
Published on: August 18, 2014
GluR1-immunopositive interneurons in rat neocortex
V N Kharazia1, R J Wenthold, R J Weinberg
1Department of Cell Biology and Anatomy, University of North Carolina, Chapel Hill 27599, USA. kharazia@med.unc.edu
Insights
Inhibitory interneurons in the rat cortex possess calcium-permeable alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) channels due to GluR1 subunit expression without GluR2. This finding impacts neuronal function and excitotoxic vulnerability.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- In vitro studies suggest inhibitory interneurons express GluR1 without GluR2, forming calcium-permeable AMPA channels.
- The functional implications and cellular localization of these channels in vivo remain to be fully elucidated.
Purpose of the Study:
- To confirm and extend in vitro findings on GluR1 expression in rat cortical inhibitory interneurons.
- To investigate the cellular localization and potential functional consequences of calcium-permeable AMPA channels in these neurons.
Main Methods:
- Quantitative immunocytochemistry for multiple antigens in rat somatic sensory cortex.
- Electron microscopy to analyze subcellular localization of GluR1.
- Double immunostaining to identify neuronal populations expressing GluR1 and GABAergic markers.
Main Results:
- A distinct subpopulation of nonpyramidal neurons showed intense GluR1 immunoreactivity.
- GluR1 was localized to the somatic rough endoplasmic reticulum and dendritic active zones.
- The majority of GluR1-positive neurons were GABAergic, containing little or no GluR2.
Conclusions:
- Cortical inhibitory interneurons likely possess calcium-permeable AMPA receptors.
- This calcium permeability may influence neuronal function, calcium-binding protein expression, and excitotoxic susceptibility.
Abstract:
Recent in vitro studies suggest that inhibitory interneurons in cortex may express the GluR1 glutamate receptor subunit in the absence of GluR2, leading to calcium-permeable alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) channels. We performed a study of rat somatic sensory cortex to confirm and extend these observations, using quantitative immunocytochemistry for multiple antigens. A morphologically distinct subpopulation of nonpyramidal neurons in neocortex was intensely immunoreactive for GluR1. Electron microscopic analysis of these cells revealed somatic staining for GluR1, mainly in the rough endoplasmic reticulum. Dendritic staining was concentrated at the synaptic active zone and in the adjacent subsynaptic cytoplasm. Double immunostaining revealed that the large majority of intensely GluR1-positive cells contained gamma-aminobutyric acid or its synthetic enzyme, glutamic acid decarboxylase, but little or no GluR2. Thus, AMPA receptors on a subpopulation of inhibitory interneurons in cortex are likely to be calcium permeable. This calcium permeability is likely to influence functional properties of these neurons; it may underlie the high levels of calcium-binding proteins they contain; and may render them liable to excitotoxic injury
