The authors have demonstrated the estradiol induction of the key glycolytic enzymes of the brain (hexokinase, phosphofructokinase and pyruvate kinase) which is "switched off" by injection of actinomycin-D--an inhibitor of protein biosynthesis. Another steroid hormone, progesterone, has an inhibitory action on the above enzymes. Administration of estradiol to rats significantly elevates the amplitude and frequency of contractility induced in them, while the same doses of progesterone decrease them. Thus, there is a definite correlation between the induction of glycolytic enzymes and sensitivity toward contractility on the one hand and the estradiol/progesterone ratio on the other. It is possible that activation of glycolysis may reduce the threshold of epileptic attacks providing an additional energy for epileptic manifestations.