Effects of Inorganic and Organic Mercury
on Cortical and Hippocampal Activity in Rats
András Papp, Tünde Vezér, and László Pecze
Department of Public Health, University of Szeged, Hungary
Corresponding author: András Papp
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: ppp@puhe.szote.u-szeged.hu
CEJOEM 2002, Vol.8. No.2–3.:118–125
Key words:
Inorganic mercury, organic mercury, cortex, hippocampus, rat, neurotoxicity
Abstract:
People are exposed to inorganic or organic mercury in various occupational and environmental
settings. The aim of this study was to see the effect of an inorganic and an organic mercury
compound on spontaneous and stimulus-evoked central nervous activity in rats under identical
experimental conditions. Male Wistar rats were treated for 10 weeks with 0.5 and 2.0 mg/kg b.w. of
mercuric chloride (HgCl2) or methylmercury chloride (CH3HgCl) per os by
gavage. For neurophysiological investigation, the animals were anaesthetised, placed in a
stereotaxic instrument, and the left hemisphere was exposed. Activity was recorded from the
primary somatosensory, visual and auditory fields, and the hippocampal CA1 region. There was no
qualitative difference between the effects of inorganic and organic mercury but the same dose of
methylmercury generally elicited more marked alterations. In the spontaneous cortical and
hippocampal activity, the peak of activity was shifted to higher frequencies. The duration of the
somatosensory and visual cortical evoked potentials were significantly shortened by organic but
hardly affected by inorganic mercury. Methylmercury had a stronger effect on the tetanic
potentiation of hippocampal evoked activity (population spike) than mercury chloride had. Our
results indicate that differences in chemical character and neurotoxicity are only partially in line.
Received: 3 July 2002
Accepted: 12 September 2002
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