Reduction of KCC2 expression and GABAA receptor-mediated excitation after in vivo axonal injury
| Autor: | Norio Akaike, Atsuo Fukuda, Toru Iwaki, Akihiko Okabe, Junichi Nabekura, Tsuyoshi Ueno, Chigusa Shimizu-Okabe, Akiko Furuta |
|---|---|
| Rok vydání: | 2002 |
| Předmět: |
Patch-Clamp Techniques
medicine.medical_treatment Vagotomy Membrane Potentials GABA Antagonists GABA chemistry.chemical_compound Nickel NKCC1 Diuretics motoneuron In Situ Hybridization Motor Neurons Sulfonamides Symporters GABAA receptor Muscimol General Neuroscience Axotomy Ca2+ Excitatory postsynaptic potential Bumetanide Cl medicine.drug Tetrodotoxin Biology In Vitro Techniques Inhibitory postsynaptic potential Chlorides medicine Animals GABA-A Receptor Agonists GABA-A Receptor Antagonists RNA Messenger ARTICLE GABA Agonists Fluorescent Dyes excitation Bicuculline Receptors GABA-A Axons Rats chemistry nervous system Biophysics Calcium Cotransporter Neuroscience |
| Zdroj: | Scopus-Elsevier |
| ISSN: | 1529-2401 |
| Popis: | After axotomy, application of muscimol, a GABA(A) receptor agonist, induced an increase in intracellular Ca(2+) ([Ca(2+)](i)) in dorsal motor neurons of the vagus (DMV neurons). Elevation of [Ca(2+)](i) by muscimol was blocked by bicuculline, tetrodotoxin, and Ni(2+). In axotomized DMV neurons measured with gramicidin perforated-patch recordings, reversal potentials of the GABA(A) receptor-mediated response, presumably equal to the equilibrium potential of Cl(-), were more depolarized than that in intact neurons. Thus, GABA(A) receptor-mediated excitation is suggested to be attributable to Cl(-) efflux out of the cell because of increased intracellular Cl(-) concentration ([Cl(-)](i)) in axotomized neurons. Regulation of [Cl(-)](i) in both control and injured neurons was disturbed by furosemide and bumetanide and by manipulating cation balance across the membrane, suggesting that functional alteration of furosemide-sensitive cation-Cl(-) cotransporters is responsible for the increase of [Cl(-)](i) after axotomy. In situ hybridization revealed that neuron-specific K(+)-Cl(-) cotransporter (KCC2) mRNA was significantly reduced in the DMV after axotomy compared with that in control neurons. Similar expression of Na(+), K(+)-Cl(-) cotransporter mRNA was observed between axotomized and control DMV neurons. Thus, axotomy led to disruption of [Cl(-)](i) regulation attributable to a decrease of KCC2 expression, elevation of intracellular Cl(-), and an excitatory response to GABA. A switch of GABA action from inhibitory to excitatory might be a mechanism contributing to excitotoxicity in injured neurons. |
| Databáze: | OpenAIRE |
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