Changes in Intracellular Chloride after Oxygen-Glucose Deprivation of the Adult Hippocampal Slice: Effect of Diazepam

• Published in: The Journal of neuroscience Vol. 24; no. 18; pp. 4478 - 4488
• Main Authors: Galeffi, Francesca, Sah, Renu, Pond, Brooks B, George, Amanda, Schwartz-Bloom, Rochelle D
• Format: Journal Article
• Language: English
• Published: United States Soc Neuroscience 05.05.2004; Society for Neuroscience
• Subjects: Action Potentials - drug effects; Action Potentials - physiology; Animals; Brain Ischemia - metabolism; Brain Ischemia - pathology; Calcium - metabolism; Cell Hypoxia - physiology; Chlorides - metabolism; Diazepam - pharmacology; GABA Antagonists - pharmacology; Glucose - deficiency; Glucose - metabolism; Hippocampus - drug effects; Hippocampus - pathology; Hippocampus - physiopathology; In Vitro Techniques; Intracellular Fluid - metabolism; K Cl- Cotransporters; Male; Neurobiology of Disease; Neurons - drug effects; Neurons - metabolism; Neurons - pathology; Neuroprotective Agents - pharmacology; Quinolinium Compounds; Rats; Rats, Sprague-Dawley; Receptors, GABA-A - drug effects; Receptors, GABA-A - metabolism; Recovery of Function - drug effects; Recovery of Function - physiology; Sodium-Potassium-Chloride Symporters - metabolism; Solute Carrier Family 12, Member 2; Symporters - metabolism; Synaptic Transmission - drug effects; Synaptic Transmission - physiology
• ISSN: 0270-6474; 1529-2401; 1529-2401
• DOI: 10.1523/JNEUROSCI.0755-04.2004

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