The effects of imidazole-4-acetic acid on cerebral carbohydrate metabolism

The effects of intravenous administration of 50-400 mg/kg imidazole-4-acetic acid (IMA) on the carbohydrate metabolism of the rat brain were assessed by measurement of the cerebral hemisphere contents of energy phosphates and glycolytic--citric acid cycle metabolites. IMA (100-400 mg/kg) produced a spectrum of electroencephalographic (EEG) change ranging from desynchronization to electrical suppression which was associated with unchanged tissue contents of ATP, ADP, and AMP, increasing levels of phosphocreatine, glucose, and aspartate, and decreasing levels of pyruvate, lactate, alpha-ketoglutarate, and malate. The changes in glycolytic intermediates were present within 5 min of injecting IMA (200 mg/kg) and the pattern suggested a suppression of glycolysis. The EEG stage of electrical suppression with episodic spiking (400 mg/kg) was associated with a 30% reduction of cortical high-energy phosphate use. The lowest dose of IMA (50 mg/kg) resulted in episodic EEG desynchronization which was associated with no significant changes of the measured metabolites. The results indicate that IMA is associated with metabolite changes that are compatible with a state of cerebral depression and that the desynchronous EEG pattern is without a biochemical correlate of increased neuronal activity.