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Excitatory actions of GABA in the cortex
Allan T Gulledge1, Greg J Stuart
1Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Mills Road, Canberra, ACT 0200, Australia.
Neuron
|January 28, 2003
Summary
Gamma-aminobutyric acid (GABA) can excite cortical neurons, not just inhibit them. This excitatory effect occurs when GABAergic inputs are isolated from excitatory inputs, influencing action potential generation.
Area of Science:
- Neuroscience
- Cellular Electrophysiology
- Synaptic Plasticity
Background:
- The role of gamma-aminobutyric acid (GABA) in neuronal inhibition is well-established.
- Understanding GABAergic and excitatory input interactions under physiological conditions is crucial.
- Little is known about GABAergic input effects when intracellular anion concentrations are maintained.
Purpose of the Study:
- To investigate the interaction between GABAergic and excitatory inputs in cortical pyramidal neurons.
- To determine the conditions under which GABAergic inputs exert excitatory effects.
- To elucidate the role of GABA in synaptic integration within the cortex.
Main Methods:
- Extracellular field potential recordings.
- Gramicidin perforated-patch clamp recordings from mature cortical pyramidal neurons.
- Analysis of somatic and dendritic GABA responses in relation to excitatory inputs.
Main Results:
- Both somatic and dendritic GABA responses were depolarizing from rest in mature cortical pyramidal neurons.
- Dendritic GABA responses were consistently excitatory.
- Somatic GABA responses were inhibitory when coincident with excitatory input but excitatory at earlier times, facilitating action potential generation.
Conclusions:
- GABAergic inputs can have an excitatory role in cortical synaptic integration.
- The excitatory action of GABA occurs even when its reversal potential is below action potential threshold.
- Temporal or spatial isolation of GABAergic inputs from concurrent excitation leads to excitatory effects.