Changes in intracellular chloride after oxygen-glucose deprivation of the adult hippocampal slice: effect of diazepam.
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
Galeffi
Francesca
F
Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Sah
Renu
R
Pond
Brooks B
BB
George
Amanda
A
Schwartz-Bloom
Rochelle D
RD
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism* / Q000473:pathology; D002118:Calcium / Q000378:metabolism; D015687:Cell Hypoxia / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism*; D003975:Diazepam / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D005947:Glucose / Q000172:deficiency / Q000378:metabolism*; D006624:Hippocampus / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000378:metabolism*; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology; D011806:Quinolinium Compounds; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism; D020127:Recovery of Function / Q000187:drug effects / Q000502:physiology; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism; D064506:Solute Carrier Family 12, Member 2; D027981:Symporters / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D000096922:K Cl- Cotransporters
D002118:Calcium; D002712:Chlorides; D003975:Diazepam; D018756:GABA Antagonists; D005947:Glucose; D018696:Neuroprotective Agents; D011806:Quinolinium Compounds; D011963:Receptors, GABA-A; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D027981:Symporters; D000096922:K Cl- Cotransporters; C578879:Slc12a2 protein, rat; C070311:6-methoxy-N-ethylquinolinium