Elektroenzephalographische und psychoexperimentelle Untersuchungen mit Lithium an gesunden Probanden

Abstract

In previous experiments with lithium on normal volunteers, in whom plasma levels of 0.8 mmol/l after acute and 0.5-0.6 mmol/l during steady state after two weeks of lithium administration were obtained, we found slight effects on the awake EEG and psychological performance tests which could be interpreted as a decrease in vigilance and activation. The present study was designed to replicate these results with slightly higher plasma levels: 1 mval/l (acute), an 0.7-0.9 mval/l during steady state, in normal subjects selected according to strict EEG criteria. Besides quantitative pharmaco-EEG, the Zerssen scale for mood (Bf-S) and psychosomatic complaints (B-L) were applied; furthermore, subjective time estimation, the digit symbol test, flicker fusion frequency, and the pursuit rotor test were performed. After acute administration only a slight increase in psychosomatic complaints and a tendency towards increase in xxx-power in the EEG could be observed. Under chronic lithium treatment a significant increase in xxx-power and decrease in flicker fusion frequency in comparison to placebo were found. Tendencies for a decrease in performance were obtained by the digit symbol test and by the pursuit rotor test. The subjective time estimation 17 seconds as well as mood and psychosomatic complaints as measured by Bf-S and B-L did not change. The results of this trial confirm that lithium has negative effects on vigilance and activation. However, despite of higher plasma levels, the changes found in comparison to placebo were slight and discrete. Thus, in the routine test battery designed to describe and classify acute effects of classic psychotropic drugs such as 10 mg diazepam, 75 mg chlorpromazinc, 75 mg imipramine, or 20 mg dextroamphetamine, lithium does not induce unambiguous effects. Other test models are required to demonstrate specific psychic effects of lithium. In this context, appropriate criteria for selection of lithium sensitive subjects play an important role.