Effects of prenatal methylmercury exposure on brain monoamine oxidase activity and neurobehaviour of rats.
Monoamine oxidase (MAO) regulates levels of dopamine, serotonin, and noradrenaline in the nervous tissue and is required for proper neuronal development. The purpose of this study was to determine if oral exposure of adult female rats to methylmercury (MeHg) at 0.5 or 1 mg/kg/day before and during pregnancy would affect MAO activity in various brain regions of the offspring. Offspring neurobehaviour performance was also assessed. The brain MAO activity of female offspring was reduced at both MeHg doses with significantly lower values noted in the brainstem region. No significant MeHg dose effects on MAO activity were observed in the male offspring. Neurobehavioural evaluations indicated that MeHg exposure altered auditory startle in the female offspring. Rat whole embryos (gestational day 13.5) cultured with 750 microg/L MeHg in vitro significantly decreased total MAO activity by 15%. In conclusion, this study demonstrated that exposure to MeHg in rats before and/or during gestation resulted in a reduction of MAO activity in the developing embryo and brainstem of the female offspring with accompanying changes in auditory startle response. Evaluation of MAO activity may serve as an indicator for neurotoxicity following developmental exposure to MeHg and should be further investigated.
Beyrouty
Peter
P
Centre for Indigenous Peoples' Nutrition and Environment, Macdonald Campus of McGill University, Ste-Anne-de-Bellevue, Quebec, Canada, H9X-3V9.
Stamler
Christopher J
CJ
Liu
Jiun-Ni
JN
Loua
Kovana Marcel
KM
Kubow
Stan
S
Chan
Hing Man
HM
D000161:Acoustic Stimulation / Q000379:methods; D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001923:Brain Chemistry / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004622:Embryo, Mammalian; D005260:Female; D008297:Male; D008767:Methylmercury Compounds / Q000378:metabolism / Q000633:toxicity*; D008995:Monoamine Oxidase / Q000378:metabolism*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011597:Psychomotor Performance / Q000187:drug effects; D051381:Rats; D013216:Reflex, Startle / Q000187:drug effects*; D012737:Sex Factors
D008767:Methylmercury Compounds; D008995:Monoamine Oxidase