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A Method for High Fidelity Optogenetic Control of Individual Pyramidal Neurons In vivo
Published on: September 2, 2013
Kv2 channels regulate firing rate in pyramidal neurons from rat sensorimotor cortex
Dongxu Guan1, William E Armstrong, Robert C Foehring
1R. C. Foehring: Department of Anatomy & Neurobiology, University of Tennessee Health Science Center, 855 Monroe Avenue, Memphis, TN 38163, USA. rfoehrin@ithsc.edu.
The Journal of Physiology
|July 24, 2013
Summary
Kv2.1 potassium channels regulate neuronal firing in the neocortex. Inhibiting Kv2.1 channels reduces firing rate and increases spike frequency adaptation by altering membrane potential during interspike intervals.
Area of Science:
- Neuroscience
- Molecular Biology
- Electrophysiology
Background:
- The primary outward potassium current in neocortical pyramidal neurons involves Kv2.1 alpha subunits.
- Kv2.1 channels are implicated in neuronal responses to seizures, ischemia, plasticity, cell death, and anesthesia.
- Limited knowledge of Kv2 channel function exists due to a lack of specific pharmacological agents.
Purpose of the Study:
- To investigate the functional roles of Kv2 channels in rat somatosensory and motor cortex pyramidal neurons (layers 2/3 and 5).
- To manipulate Kv2 channel expression using a Kv2.1 pore mutant (Kv2.1 DN) in an organotypic culture model.
- To assess the impact of Kv2.1 channel manipulation on neuronal excitability and firing properties.
Main Methods:
- Organotypic slice cultures from postnatal day 7-14 rats.
- Biolistic transfection of neurons with DNA for Kv2.1 DN, wild-type Kv2.1, or green fluorescent protein (GFP).
- Whole-cell voltage-clamp and current-clamp recordings to measure potassium currents and neuronal firing properties.
Main Results:
- Transfection with Kv2.1 DN significantly reduced outward potassium current density by approximately 45%.
- Overexpression of wild-type Kv2.1 greatly increased outward currents, while GFP alone had no effect.
- Kv2.1 DN expression reduced firing rate and steady-state gain, while increasing spike frequency adaptation.
Conclusions:
- Kv2 channels play a crucial role in controlling membrane potential during interspike intervals.
- The absence of functional Kv2 channels leads to sustained depolarization, preventing sodium channel recovery from inactivation.
- This mechanism explains the observed decrease in firing rate and enhanced spike frequency adaptation in Kv2.1 DN cells.
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