Changes in intracellular chloride after oxygen-glucose deprivation of the adult hippocampal slice: effect of diazepam.

Journal Article

Ischemic injury to the CNS results in loss of ionic homeostasis and the development of neuronal death. An increase in intracellular Ca2+ is well established, but there are few studies of changes in intracellular Cl- ([Cl-]i) after ischemia. We used an in vitro model of cerebral ischemia (oxygen-glucose deprivation) to examine changes in [Cl-]i and GABA(A) receptor-mediated responses in hippocampal slices from adult rats. Changes in [Cl-]i were measured in area CA1 pyramidal neurons using optical imaging of 6-methoxy-N-ethylquinolinium chloride, a Cl--sensitive fluorescent indicator. Oxygen-glucose deprivation induced an immediate rise in [Cl-]i, which recovered within 20 min. A second and more prolonged rise in [Cl-]i occurred within the next hour, during which postsynaptic field potentials failed to recover. The sustained increase in [Cl-]i was not blocked by GABA(A) receptor antagonists. However, oxygen-glucose deprivation caused a progressive downregulation of the K+-Cl- cotransporter (KCC2), which may have contributed to the Cl- accumulation. The rise in [Cl-]i was accompanied by an inability of the GABA(A) agonist muscimol to cause Cl- influx. In vivo, diazepam is neuroprotective when given early after ischemia, although the mechanism by which this occurs is not well understood. Here, we added diazepam early after oxygen-glucose deprivation and prevented the downregulation of KCC2 and the accumulation of [Cl-]i. Consequently, both GABA(A) responses and synaptic transmission within the hippocampus were restored. Thus, after oxygen-glucose deprivation, diazepam may decrease neuronal excitability, thereby reducing the energy demands of the neuron. This may prevent the activation of downstream cell death mechanisms and restore Cl- homeostasis and neuronal function

Full Text

Duke Authors

Cited Authors

  • Galeffi, F; Sah, R; Pond, BB; George, A; Schwartz-Bloom, RD

Published Date

  • May 5, 2004

Published In

Volume / Issue

  • 24 / 18

Start / End Page

  • 4478 - 4488

PubMed ID

  • 15128862

Electronic International Standard Serial Number (EISSN)

  • 1529-2401

Digital Object Identifier (DOI)

  • 10.1523/JNEUROSCI.0755-04.2004

Language

  • eng

Conference Location

  • United States