塩化メチル水銀による,ラット自発行動量のウルトラディアンリズムへの影響

概要

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The present study was undertaken to investigate the effects of methylmercuric chloride (MMC) on the rhythms of the locomotor activity in rats.The food administered to experimental male rats contaided MMC. The locomotor activities of MMC-treated and control rats were determined using an ANIMEX-III A in light-dark (12:12) cycles and calculated with spectral analysis (by fast Fourier transform).The following results were obtained:(1) The daily locomotor activities in MMC-treated rats decreased for the first 21 days, and then increased after that.(2) In locomotor activity, distinct 12-, 8-, and 4.8-hr ultradian rhythms were found in the power spectrum of the control rats.(3) The disappearance of the 8-hr ultradian rhythm immediately before the onset of hind-leg crossing and the enhancement of ultradian rhythms with 1-3hr periodicity after the onset of hind-leg crossing were observed in the power spectrum of MMC-treated rats.These results indicate that the disappearance of the 8-hr rhythm in the power spectrum is a significant sign of methylmercury poisoning and that the analysis of ultradian rhythms might be useful in the study of heavy metal toxicology.