The glutamatergic component of the piracetam effect upon the EEG frequency spectrum was studied in wakeful rats with electrodes implanted into somatosensory cortex and hippocampus and a cannula in the lateral ventricle. Piracetam at a dose of 400 mg/kg enhanced the EEG activity in the range of 10.4-16.4 Hz in two phases: early (10-40 min) and late (above 50 min). Only the late phase was retained against the background of the NMDA receptor antagonist CPP (0.1 nmole). This stage was also retained upon the subchronic administration of piracetam. The AMPA-receptor agonist quisqualate (5 nmole) enhanced the EEG power in the range of 1.5-5 Hz and decreased the activity at 10.4-16.4 Hz. The AMPA-receptor antagonist glutamate diethyl ester (1 mumole) leveled the agonist effect, but enhanced the piracetam action in the late phase at frequencies in the alpha range.