Protective effect of sevoflurane preconditioning on oxygen-glucose deprivation injury in rat hippocampal slices: the role of mitochondrial K(ATP) channels / 生理学报

To investigate the neuroprotective effects of sevoflurane preconditioning on oxygen-glucose deprivation (OGD) injury and the role of mitochondrial KATP channels in rat, we established OGD injury model in rat hippocampal slices. The brain was rapidly removed, and the dissected hippocampus was sliced in cold artificial cerebrospinal fluid (ACSF) transversely to its longitudinal axis (400 mum thick) with a Rotorslicer DTY-7700. Slices were placed on a nylon mesh in a recording chamber at 34 degrees C and humidified gas mixture (95% O2/5% CO2) was applied to the chamber at a flow rate of 200 ml/min. After 2 h of incubation, slices were randomly exposed to 2%, 4%, 6% sevoflurane or 6% sevoflurane combined with mitochondrial K(ATP) channel blocker (5-hydroxydecanoic acid, 5-HD) under normal condition (95% O2/5% CO2) for 30 min. Fifteen minutes later, slices were exposed to 14-minute OGD followed by 1-hour reoxygenation, and the changes of orthodromic population spike (OPS) at the end of reoxygenation were measured. The changes of ultrastructure of CA1 area in the group of 14-minute OGD followed by 1-hour reoxygenation were detected with electron microscope. The results showed that sevoflurane preconditioning delayed the abolishing time of OPS (P<0.01) and significantly increased the recovery rate and the recovery amplitude of OPS compared with the OGD group. The recovery rate of OPS was 71.4% both in 4% and 6% sevoflurane preconditioning groups (P<0.05 vs OGD group), accordingly the recovery amplitude of OPS was (61.0 +/- 42.3)% and (78.7 +/- 21.1)% (P<0.01), respectively. The protective effect of 6% sevoflurane was blocked by 5-HD. Ultrastructural observation in the hippocampal CA1 region of the OGD group showed severe edema of the pyramidal cells, crimpled or ruptured nucleus membranes, aggregation of chromatin, and swelling of mitochondria, whereas these changes were less prominent in 4% and 6% sevoflurane groups. These results suggest that sevoflurane preconditioning is capable to protect neurons from OGD injury in vitro and that the protective effect is related to the activation of mitochondrial K(ATP) channels.

Relation between GLu-R and the protective effect of hypothermia on oxygen and glucose deprivation injury in hippocampal slice or rat / 中国应用生理学杂志

<p><b>AIM</b>To investigate the relation between Glu-R and the protective effect of hypothermia on oxygen and glucose deprivation (OGD) injury in hippocampal slices of rat.</p><p><b>METHODS</b>(1) We had established OGD injury model in rat hippocampal slices. The changes of orthodromic population spike(OPS) during OGD and after administration of hypothermia (32 degrees C, 25 degrees C) were observed. (2) We had established Glu excitatory toxicity injury model in rat hippocampal slices. The changes of OPS after exposure to Glu and the effect of hypothermia (32 degrees C, 25 degrees C) against the Glu excitatory toxicity injury were observed. The non-NMDA receptor-mediated excitatory postsynaptic potentials (EPSP) in the CA1 area were recorded via adding the GABA-R specific agonists bicuculline (BMI) and NMDAR agonists D-(-)-2-Amino-5-phosphonopentanoic Acid (AP5) in normal artificial cerebrospinal fluid (nACSF), the NMDA receptor-mediated EPSP were recorded via adding the BMI and non-NMDA-R agonists 6,7-Dinitroquinoxaline-2, 3(1H,4H)-dione(CNQX) in nACSF. The variety of the changes of OPS during OGD14min in nACSF groups and added BMI compounded AP5 or BMI compounded CNQX ACSF groups were observed after administration of 25 degrees C hypothermia 28 min. (3) The changes of ultrastructure of CA1 area after OGD 1 h and the effect of hypothermia (25 degrees C) on it were observed.</p><p><b>RESULTS</b>(1) OPS reduced and abolished quickly during OGD14min, and the recovery amplitude of OPS was very low after reoxygenation/glucose 1 h. While the time of OPS abolishing significantly elongated and the recovery of OPS was higher in hypothermia (32 degrees, 25 degrees C) groups. The effect in groups 25 degrees C was more significant than those in groups 32 degrees C. (2) In control groups, Glu (2 mmol/L, 14 min) decreased the amplitude of OPS, after the end of Glu exposure the recovery amplitude of OPS was very low. After administration of hypothermia (32 degrees C, 25 degrees C), the recovery amplitude and rate of OPS were significantly higher than those in the control groups, while the antagonism on Glu excitatory toxicity injury in H 25 degrees C was more significant than those in H 32 degrees C. The changes of OPS during OGD 14 min were no distinct difference in nACSF groups and added BMI (50 micromol/L) compounded AP5(20 micromol/L) or BMI (50 micromol/L) compounded CNQX (100 micromol/L) ACSF groups. The protection of hypothermia (25 degrees C) could not be cancelled by added AP5 compounded BMI or BMI compounded CNQX in nACSF. (3) After OGD (14 min) 1 h, the nuclear membrane of pyramidal cells in CA1 area was irregular, nucleus were homogenized, the organelle in the cytoplasm was degenerate, even more to necrosis or loss, mitochondrion swelled, ridge was vacuoles. In H 25 degrees C the nuclear membrane was regular, mitochondrion swelled only lightly. Small chromatin gathered to edge.</p><p><b>CONCLUSION</b>Hypothermia shows the protective effects of against OGD injury in hippocampal slices. The mechanism is related to the antagonism of Glu excitor toxicity and maintenance the ATP level in cells, and the antagonism perhaps is mediated by NMDA-R and non-NMDA-R.</p>