Nervous system disorders are among the leading symptoms of human manganese exposure of occupational or environmental origin. A number of alterations in various forms of nervous activity have been reported in humans and experimental animals but the underlying mechanisms and the relationship of effects at different organization levels are not yet fully elucidated.

In the acute experiments, cortical evoked potentials obtained with electrical stimulation of the whisker pad and the tail base, and compound action potential of the tail nerve, were recorded from adult male Wistar rats anesthetized with urethane (1000 mg/kg b.w.). After three control stimulation series (trains of 50 stimuli) in 30 min intervals, 50 mg/kg b.w. in form of MnCl₂ solution was injected ip. and further records were taken until the general deterioration of the animal. It was found that the changes in the amplitude and latency of the cortical responses evoked from the two stimulation sites were in good correlation (R²>0.7) but had no correlation to the changes of the tail nerve action potential. Consequently, the changes induced by acute Mn administration have taken place most likely within the CNS.

In the subacute experiments, a novel method was applied: simultaneous recording of electrocorticogram and motor behaviour in awake rats. The rats were equipped with a connector "crown" - allowing ECoG lead-off while the animal's motor activity was recorded in an open field cage - and had 30 min session weekly. After two control sessions, the rats were orally exposed by Mn through the drinking water (2.5 mg/ml Mn) for 4-8 weeks with continued weekly recordings. In the treatment period, the rats' total ambulation distance and time was significantly less than before Mn exposure. Also, the decrease of locomotion during a 30 min session was increased by Mn. The changes of the ECoG were less characteristic but a correlation between higher total cortical activity and lower motility was observed.

First of all the "crown" technique is promising for further neurotoxicological and neuropharmacological studies.