Changes in the Spontaneous and Evoked Cortical Activity of Rats Induced by Two Mitochondrial Toxins

Andrea Szabó, László Pecze, and András Papp

Department of Public Health, University of Szeged Faculty of Medicine, Szeged, Hungary

Corresponding author: Andrea Szabó
    Department of Public Health
    Faculty of Medicine
    University of Szeged
    Dóm tér 10.
    H-6720 Szeged, Hungary
    Telephone: +36-62-545-119
    Fax number: +36-62-545-120
    E-mail: szaboa@puhe.szote.u-szeged.hu

CEJOEM 2004, Vol.10. No.1.: 5–11

Key words:
Manganese, 3-nitropropionic acid, electrocorticogram, evoked potential, rat

Abstract:
Mitochondrial toxins are an interesting group of neurotoxicants including certain heavy metals and a number of organic compounds. In case of manganese, brain is one of the target organs, resulting in compulsive and aberrant behaviour, emotional instability and hallucinations. Mn²⁺ ions are known to interfere with certain enzymes involved in the energy-producing mitochondrial oxidation. The organic toxin 3-nitropropionic acid (3-NP) is produced by various microfungi and is found in leguminous plants used as animal feed. 3-NP causes biochemical and morphological alterations in the brain. Humans exposed to 3-NP develop seizures and coma, followed by persisting abnormalities of motion. In this study we tried to elucidate to what extent neurophysiological measurements are suitable to detect functional changes caused by acute administration of these toxicants.
    In anaesthetised male Wistar rats, a silver recording electrode was placed on the somatosensory projection area of the whiskers. The corresponding peripheral site was stimulated by weak electric pulses, and the cortical response was recorded. On the averaged records, amplitude and latency were measured. Spontaneous activity electrocorticogram (ECoG) was taken simultaneously, and the relative distribution of the activity over the bands (delta to gamma) was automatically generated.
    On intraperitoned administration of Mn²⁺ (50 mg/kg) the amplitude of the evoked response showed first a decrease then an increase. In the spontaneous cortical activity, there was a parallel shift to lower frequencies but the correlation of the two changes was moderate. Acute administration of 3-NP (20 mg/kg, ip.) decreased the amplitude of the evoked response. Its effect on the spontaneous activity was below significance.
    Due to the importance of these substances as environmental burden and as experimental tools, further investigation of their functional neurotoxic properties is justified.

Received: 19 September 2003
Accepted: 1 December 2003

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