Isoflurane neuroprotection in rat hippocampal slices decreases with aging: changes in intracellular Ca2+ regulation and N-methyl-D-aspartate receptor-mediated Ca2+ influx.
BACKGROUND
Most in vitro neuroprotection studies with isoflurane have involved cells obtained during the embryonic or early postnatal period. However, in mature rodents, isoflurane neuroprotection does not persist. The authors determined whether neuroprotection of hippocampal slices with isoflurane decreases with aging and is due to decreased intracellular Ca regulation and survival protein phosphorylation.


METHODS
Hippocampal slices from 5-day-old, 1-month-old, and 19- to 23-month-old rats were deprived of oxygen and glucose for 5-30 min in media bubbled with 1% isoflurane. Cell death was assessed in the CA1, CA3, and dentate regions, and intracellular Ca concentration was measured in CA1 neurons. N-methyl-d-aspartate receptor (NMDAR)-dependent Ca influx was measured and the phosphorylation of NMDARs, and the survival proteins Akt and mitogen-activated protein kinase p42/44 were quantified.


RESULTS
Twenty minutes of oxygen and glucose deprivation killed approximately 40-60% of neurons in CA3 and dentate in all age groups. Isoflurane, 1%, reduced death of CA1, CA3, and dentate neurons in slices from 5-day-old rats but not those from 23-month-old rats. In 5-day slices, isoflurane attenuated NMDAR-mediated Ca influx, whereas in aging slices, Ca influx was increased protein kinase C. In aging slices, isoflurane did not increase the phosphorylation of Akt and p42/44.


CONCLUSIONS
Isoflurane neuroprotection of hippocampal slices during oxygen and glucose deprivation decreases with age. Isoflurane does not prevent large increases in intracellular Ca concentration during oxygen and glucose deprivation and does not induce the phosphorylation of the prosurvival proteins in aging slices. A protein kinase C-mediated increase in NMDAR activity may result in increased excitotoxicity and decreased neuroprotection by volatile anesthetics in the aging brain.
Zhan
Xinhua
X
Severinghaus-Radiometer Research Laboratories, Department of Anesthesia and Perioperative Care, University of California at San Francisco, 94143-0542, USA.
Fahlman
Christian S
CS
Bickler
Philip E
PE
D000375:Aging / Q000502:physiology*; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D002118:Calcium / Q000502:physiology*; D020013:Calcium Signaling / Q000187:drug effects; D015687:Cell Hypoxia / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D005947:Glucose / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects* / Q000254:growth & development*; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D007530:Isoflurane / Q000494:pharmacology*; D018696:Neuroprotective Agents; D010101:Oxygen Consumption / Q000187:drug effects; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects*; D013569:Synapses / Q000187:drug effects
D018685:Anesthetics, Inhalation; D007202:Indicators and Reagents; D018696:Neuroprotective Agents; D016194:Receptors, N-Methyl-D-Aspartate; D007530:Isoflurane; D005947:Glucose; D002118:Calcium