Kinetics of sevoflurane action on GABA- and glycine-induced currents in acutely dissociated rat hippocampal neurons
Section snippets
Preparation
Pyramidal neurons were acutely dissociated from the CA1 region of the rat hippocampus. Two-week-old Wistar rats (Kyudo, Fukuoka, Japan) were decapitated under pentobarbital anaesthesia (40 mg/kg). The brain was quickly removed from the skull and sliced at a thickness of 400 μm with a microslicer (Dosaka, DTK-1000, Kyoto, Japan). The brain slices were preincubated in an incubation solution bubbled with 95% O2/5% CO2 gas at room temperature for 60 min. Thereafter, slices were treated with pronase (1
Concentration of sevoflurane in aqueous solutions
To validate our method of dissolving sevoflurane into aqueous solutions, the concentrations of sevoflurane in aqueous solutions were measured using gas chromatography. The linearity of the gas chromatographic readings was confirmed by direct injection of various amounts of sevoflurane stock standard solutions (Fig. 1A). The line represents a linear regression line with a regression coefficient of 0.99. Fig. 1B shows the measured concentrations, plotted against the nominal concentrations
Direct activation of chloride current by sevoflurane
The direct activation of ICl has been shown with various volatile anaesthetics. In cultured rat hippocampal neurons, halothane, isoflurane and enflurane induced the ICl.[42] Similarly, sevoflurane induced the ICl in acutely dissociated hippocampal CA1 pyramidal neurons.[39] The estimated single-channel conductance of sevoflurane-induced ICl was 15.3 pS, close to the main conductance of the GABAA receptor–Cl− channel complex.[39] Sevoflurane directly activated the ICl in a concentration-dependent
Acknowledgements
The authors would like to thank Dr T. Ohkura (Maruishi) for the help in measuring the sevoflurane concentrations in aqueous solutions and Dr N. Tokutomi (Kumamoto University) for helpful discussion. This study was supported by Grant-in-Aid for Encouragement of Young Scientists (No. 07770033) to N. Harata from the Ministry of Education, Science and Culture of Japan.
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