Effects of thiopental on regulatory mechanisms of brain energy metabolism.

After administration of thiopental to artificially ventilated rats, the EEG, cerebral metabolism, intracellular distribution of hexokinase activity and the thiopental concentration in brain was measured. Considering the EEG changes, the time course of thiopental action was divided into an initial stage with increased beta activity and a following second stage with reduced beta activity. The glucose-6-phosphate concentration significantly increased in the first stage and fell again to the control level with the beginning of the second stage. Furthermore, during the second stage the glucose level increased and the hexokinase activity shifted from the mitochondrially bound form to the soluble form. From these results the following conclusions were drawn: Phosphofructokinase activity appeared inhibited only during the initial stage. During the second stage comparable to the stage of surgical anesthesia, thiopental solubilizes bound hexokinase activity inhibiting thereby energy metabolism.