Classification of psychotropic drugs by rat EEG analysis: the anxiolytic profile in comparison to the antidepressant and neuroleptic profile.

Electroencephalograms were recorded from the parietal and frontal cortex of freely moving rats held in constant vigilance by placing them in a slowly turning drum. The effects of 5 clinically effective anxiolytics, buspirone, meprobamate, phenobarbital, chlordiazepoxide and diazepam, were studied after intraperitoneal injection of different doses. After on-line fast Fourier transformation of the EEG signal, the drug effects were quantified by an Analysis of Variance. This resulted in a t profile for each drug dosage. Averaging the t profiles of all dosages of a drug results in a 'drug profile'. Averaging the drug profiles of the 5 anxiolytic drugs tested results in an 'anxiolytic profile'. This profile is characterized by a power decrease from 8 to 11 Hz and above 70 Hz and a power increase from 20 to 60 Hz. The anxiolytic profile is compared with the formerly defined antidepressant and neuroleptic profiles and can be clearly distinguished from the latter two.

Classification of drugs by stereotactic recording of focal brain activity in the rat (stereo-EEG).

A new electrophysiological model is described in which different types of psychoactive drugs can be differentiated from each other in the rat. Simultaneous focal recording of electrical activity from three brain regions in the presence of accumulating drug actions is followed by a calculation of the EEG power density spectrum. Division of the spectrum into 5 frequency bands for each brain region allows to evaluate a total of 15 variables. The values obtained after the last of 8 drug dosages are taken for a stepwise discriminant analysis. A distinct separation of amphetamine, chlorpromazine, diazepam and imipramine from placebo is achieved. The discriminant function obtained will serve for further drug classification.