The influence of diazepam on the electroencephalogram-evoked potential interrelation in rats

Though being a sedative, diazepam increases beta -activity in the electroen cephalogram (EEG). Diazepam also affects auditory evoked potentials (AEPs). We investigated if the effect of diazepam on AEPs could be ascribed to its beta -increasing effect. Eight rats received vehicle and diazepam counterb alanced. AEPs were ranked in ten categories according to the percentages of beta -activity in the pre-stimulus electroencephalogram (EEG). With vehicl e, the P-29, N-51 and P-67 AEP components increased and cross-correlation c oefficients (CCCs) declined with increasing beta -activity. With diazepam A EP components and CCCs remained unchanged. All AEPs with diazepam closely r esembled the AEP of the lowest beta -category obtained with vehicle. We con clude that the effect of diazepam on AEPs can not be ascribed to its beta - enhancing effect. Diazepam disrupts the normal AEP-EEG relation such that d iazepam-effects on AEPs seem to reflect the sedative effects of diazepam an d not its beta -increasing effects. (C) 2000 Published by Elsevier Science Ireland Ltd.