Excitatory actions of GABA in the cortex.
Little is known about how GABAergic inputs interact with excitatory inputs under conditions that maintain physiological concentrations of intracellular anions. Using extracellular and gramicidin perforated-patch recording, we show that somatic and dendritic GABA responses in mature cortical pyramidal neurons are depolarizing from rest and can facilitate action potential generation when combined with proximal excitatory input. Dendritic GABA responses were excitatory regardless of timing, whereas somatic GABA responses were inhibitory when coincident with excitatory input but excitatory at earlier times. These excitatory actions of GABA occur even though the GABA reversal potential is below action potential threshold and largely uniform across the somato-dendritic axis, and arise when GABAergic inputs are temporally or spatially isolated from concurrent excitation. Our findings demonstrate that under certain circumstances GABA will have an excitatory role in synaptic integration in the cortex.
Gulledge
Allan T
AT
Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Mills Road, Canberra, ACT 0200, Australia.
Stuart
Greg J
GJ
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002540:Cerebral Cortex / Q000502:physiology*; D003712:Dendrites / Q000502:physiology; D004594:Electrophysiology; D018846:Excitatory Amino Acids / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D006096:Gramicidin; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D018846:Excitatory Amino Acids; D011963:Receptors, GABA-A; D006096:Gramicidin; D005680:gamma-Aminobutyric Acid