Fig. 1.
Experimental paradigm to examine the effects of sevoflurane-induced preconditioning. Hippocampal slices were maintained in oxygenated (95% O2–5% CO2; normoxia) artificial cerebrospinal fluid (aCSF) at room temperature for 30 min and then slowly heated to 37°C. The slices were pretreated for either 15 or 60 min with 4% sevoflurane in 95% O2–5% CO2 (sevo/normoxia); only the 60-min treatment is shown. The anesthetic was washed out for 5 min with 95% O2–5% CO2 and then subjected to either 5 or 10 min of hypoxia (95% N2–5% CO2). The sevoflurane was administered using a calibrated sevoflurane vaporizer in line with the 95% O2–5% CO2 gas mixture before the aerator oxygenating the aCSF. Normoxic untreated control tissue was maintained at 37°C in oxygenated aCSF following the initial 30-min period at room temperature. A preconditioned normoxic control group was maintained under oxygenated aCSF and exposed to 4% sevoflurane in the absence of an ischemic event. The time in which the control group was exposed to sevoflurane matched the corresponding sevoflurane time in the preconditioned trial group. At the end of the sodium and potassium experiments, the slices were placed in ice-cold (2–4°C) isotonic sucrose for 10 min to wash out the extracellular ions. In the adenosine triphosphate (ATP) experiments, the slices were immediately frozen in liquid nitrogen at the end of the experiment and were not washed in sucrose.