The anti epileptic vigabatrin induces in the EEG of rats behaviour-independent increase of delta - and decrease of beta power

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Vigabatrin and diazepam both are GABAergic drugs. Vigabatrin enhances the concentration of endogenous GABA by inhibiting GABA-transaminase, while diazepam enhances the efficacy of the endogenous GABA present. As may be expected, the clinical effects of the two drugs overlap: e.g. both have anti-epileptic effects and both decrease the level of vigilance. The similarity of the effects on the EEG is however less clear. During slow-wave sleep, in drug-free rats, the EEG consists of high-voltage delta waves. Despite the induction of sleep, diazepam enhances the power of the high frequency beta band. This phenomenon is called pharmacological dissociation. In contrast, vigabatrin has been shown to slow down the EEG; the power in the delta and theta bands increases while that of the beta band decreases. However in those studies behavioural changes were not taken into consideration. The aim of the present study was to investigate, in the rat, the effect of vigabatrin on behaviour and on behaviour-related EEG.