THE EFFECT OF THE VOLATILE ANESTHETIC ISOFLURANE ON CA2-DEPENDENT GLUTAMATE RELEASE FROM RAT CEREBRAL-CORTEX()

A major effect of volatile anesthetics is to reduce excitatory synapti c transmission. In the present study the stimulated release of glutama te under the influence of increasing concentrations of isoflurane was studied in vitro by utilizing hippocampal slices from Wistar rats. Ca2 +-dependent release was calculated by subtracting stimulated release w ith blocked synaptic transmission (50 mM K+, 0 mM Ca2+ and 4 mM Mg2+) from total evoked release (50 mM K+, 2 mM Ca2+ and 1 mM Mg2+). Isoflur ane 0.51, 1.5 and 3% reduced Ca2+-dependent release of glutamate to 69 , 58 and 49%, respectively (P < 0.05 for all related to control). Thes e results are in agreement with the possibility of reduced release of transmitter as a mechanism of action of volatile anesthetics.