Journal article
Carrier-Mediated GABA Release Activates GABA Receptors on Hippocampal Neurons
Journal of neurophysiology, Vol.80(1), pp.270-281
07/01/1998
DOI: 10.1152/jn.1998.80.1.270
PMID: 9658049
Abstract
Gaspary, Heidi L., Wengang Wang, and George B. Richerson. Carrier-mediated GABA release activates GABA receptors on hippocampal neurons. J. Neurophysiol. 80: 270–281, 1998. γ-Aminobutyric acid (GABA) transporters are electrogenic and sodium-dependent and can operate in reverse when cells are depolarized or when there is reversal of the inward sodium gradient. However, the functional relevance of this phenomenon is unclear. We have examined whether depolarization induced by a physiologically relevant increase in extracellular [K+] leads to sufficient amounts of carrier-mediated GABA release to activate GABAA receptors on neurons. Patch-clamp recordings were made from rat hippocampal neurons in culture with solutions designed to isolate chloride currents in the recorded neuron. Pressure microejection was used to increase extracellular [K+] from 3 to 12 mM. After blockade of vesicular GABA release by removal of extracellular calcium, this stimulus induced a large conductance increase in hippocampal neurons [18.9 ± 6.8 (SD) nS; n = 16]. This was blocked by the GABAA receptor antagonists picrotoxin and bicuculline and had a reversal potential that followed the Nernst potential for chloride, indicating that it was mediated by GABAA receptor activation. Similar responses occurred after block of vesicular neurotransmitter release by tetanus toxin. GABAA receptors also were activated when an increase in extracellular [K+] (from 3 to 13 mM) was combined with a reduction in extracellular [Na+] or when cells were exposed to a decrease in extracellular [Na+] alone. These results indicate that depolarization and/or reversal of the Na+ gradient activated GABA receptors via release of GABA from neighboring cells. We found that the GABA transporter antagonists 1-(4,4-diphenyl-3-butenyl)-3-piperidinecarboxylic acid hydrochloride (SKF89976A; 20–100 μM) and 1-(2-{[(diphenylmethylene)amino]oxy}ethyl) -1, 2, 5, 6 - tetrahydro - 3 - pyridine - carboxylic acid hydrochloride (NO-711; 10 μM) both decreased the responses, indicating that the release of GABA resulted from reversal of the GABA transporter. We propose that carrier-mediated GABA release occurs in vivo during high-frequency neuronal firing and seizures, and dynamically modulates inhibitory tone.
Details
- Title: Subtitle
- Carrier-Mediated GABA Release Activates GABA Receptors on Hippocampal Neurons
- Creators
- Heidi L Gaspary - Yale University, New Haven, Connecticut 06510Wengang Wang - Yale University, New Haven, Connecticut 06510George B Richerson - Department of Neurology, Veteran's Affairs Medical Center, West Haven 06516; and, Yale University, New Haven, Connecticut 06510
- Resource Type
- Journal article
- Publication Details
- Journal of neurophysiology, Vol.80(1), pp.270-281
- DOI
- 10.1152/jn.1998.80.1.270
- PMID
- 9658049
- ISSN
- 0022-3077
- eISSN
- 1522-1598
- Language
- English
- Date published
- 07/01/1998
- Academic Unit
- Neurology; Molecular Physiology and Biophysics; Iowa Neuroscience Institute; Neurosurgery
- Record Identifier
- 9984020881502771
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