Behavioral Toxicology of Mercury Compounds
The spectrum of mercury toxicity is vastly wide. Much concern has been given to behavioral effects of mercury compounds. Among the mercury compounds, the effects of mercury vapor or methylmercury compounds on behavior have been well recognized in both human intoxication cases and animal experiments. Because of the readiness of mercury vapor and methylmercury crossing the placental barrier, as well as the blood brain barrier, in utero exposure of fetuses to mercury vapor or methylmercury is possible. The newborns, thus exposed, may demonstrate behavioral consequences of the exposure during the postpartum period. Epidemiological data on Minamata disease suggest that fetuses are at greater risk from methylmercury poisoning than adults. The first animal model of methylmercury poisoning after in utero exposure was demonstrated by Spyker in 1972. The behavioral consequences of in utero exposure to a toxic substance is the research interest of behavioral teratology. The term behavioral teratology was coined in 1963 to refer to the postnatal effects of prenatal exposure to drugs. Since the pioneer work by Spyker, numerous papers have been published on the behavioral teratological effects of methylmercury in experimental animals.
The work reported here is mainly concerned with behavioral teratology of methylmercury with special reference to the possibility of modifying effects of selenite on methylmercury toxicity. (1). Pregnant mice were given 30 micromoles/kg of methylmercury with (MeHgxSe) or without (MeHg) equimolar selenite on day 9 of gestation. Pups were observed postpartum days 1, 3 and 8, and evaluated for the development of righting reflex and walking activity. The results indicated decreased developmental scores in the MeHg group on days 1 and 3, and statistical analyses suggested the interaction of selenite. (2). Pregnant mice fed selenium deficient pellets from day 3 of gestation through the gestational period were allowed to litter and the deficient food was given until the weaning of the pups. The pups were examined at the age of 3 months for shock avoidance. Numbers of avoidance in a series of repeated sessions were not different from those of the pups born to the maternal mice given selenite-added drinking water. Contrary to anticipations the effects of selenite on methylmercury behavioral teratological toxicity was not clearly demonstrated. More studies are needed to conclude the possibility of modifying effects of selenite on methylmercury toxicity manifested as behavioral teratological consequences.
KeywordsMercury Concentration Prenatal Exposure Lever Press Mercury Vapor Mercury Compound
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- Spyker, J.M., Spaber, S.B. and Goldberg, A.M., 1972. Subtle consequences of methylmercury exposure: Behavioral deviation in offspring of treated mothers. Science 621-623.Google Scholar