Abstract The present study evaluated the behavioral and electroencephalographic activity induced by imidazoleacteic acid in unrestrained rats and mice. The results indicate that imidazoleacetic acid has central nervous system excitant properties similar to gamma-hydroxybutyrate. This activity was potentiated by pentylenetetrazol, picrotoxin, and strychnine. The apparent prolongation of phenobarbitone sleeping time following imidazoleacetic acid appears to be related to the induction of a cataleptoid state. The actions of imidazoleacetic acid and gammahydroxybutyrate were antagonized by caffeine. The possible relationship of these findings to energy supply for neuronal membrane function is discussed.