Parallel Changes of the Spontaneous and Stimulus-evoked Corical Activity Elicited by Acute Treatment with Inorganic Mercury in Rats

László Pecze and András Papp

Department of Public Health, University of Szeged, Hungary

Corresponding author: László Pecze
    Department of Public Health
    University of Szeged
    Dóm tér 10.
    H-6720 Szeged, Hungary
    Telephone: +36-62-545-119
    Fax number: +36-62-545-120
    E-mail address: pec@puhe.szote.u-szeged.hu

CEJOEM 2002, Vol.8. No.2–3.:126–130

Key words:
Mercury, cortex, electrocorticogram, sensory evoked potential, rat

Abstract:
Mercury is known to affect the activity of the nervous system of animals and humans, as indicated by the multitude of neurological signs following, e.g., occupational exposure. In animal experiments, heavy metals cause a variety of alterations in the central and peripheral nervous system activity but an explanation as to mechanism of action is missing in a number of cases. The aim of the work presented was to find correlation between the changes of spontaneous cortical activity (electrocorticogram, ECoG) and cortical sensory evoked potentials (EPs) recorded from rats acutely treated with mercuric chloride. Adult male Wistar rats were anesthesized with urethane. Silver recording electrodes were placed on the exposed left somatosensory projection area of the whiskers and of the tail. The corresponding peripheral sites were stimulated by electric pulses. During tail stimulation, compound action potentials of the tail nerve were also recorded. After at least 4 control records, mercury (HgCl₂, 7 mg/kg) was administered via a peritoneal cannula and the recording was continued for further ca. 2 hours. In the spontaneous activity, increased activity of the low and decreased activity of the high frequency bands was seen Simultaneously, the amplitude of the EPs increased. On the tail nerve potential, Hg caused an amplitude decrease and a latency increase. Latency increase of the cortical EP and the decrease of nerve conduction velocity evolved simultaneously. The alterations are likely due to some specific, and not to a general toxic, effect of Hg.

Received: 3 July 2002
Accepted: 12 September 2002

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