1 The electroencephalographic (EEG) eects of drugs interacting with dopaminergic and noradrenergic systems were studied in conscious rats. Power spectra (0 ± 30 Hz) were recorded from electrodes implanted bilaterally in the prefrontal cortex. Drug eects on EEG power were calculated as the spectral power following drug administration divided by the spectral power after vehicle administration. were dose-dependently antagonized by coadministration with moda®nil and cirazoline, but not by apomorphine. 4 In conclusion, pharmacological modulation of dopaminergic and noradrenergic transmission may result in consistent EEG changes: decreased dopaminergic or noradrenergic activity induces an increase of EEG spectral power; while increased dopaminergic or noradrenergic activity decreases EEG spectral power.