Behavioral effects on the progeny of mice treated with methylmercury
Su, M.Q.; Okita, G.T.
Toxicology and Applied Pharmacology 38(1): 195-205
1976
ISSN/ISBN: 0041-008X PMID: 982468 Document Number: 107190
The effects of prenatal methylmercury (MeHg) exposure on the behavior of postnatal offspring were determined in 129/SvSl mice. A single dose of 0, 6, 8, or 12 mg/kg of methylmercury hydroxide (MeHgOH) was injected s.c. to pregnant mice on day 10 of gestation. The following 3 types of behavioral tests were conducted on offspring from these mothers at various ages: exploratory behavior by open-field test at age 23 days old; spontaneous locomotor activity at ages 24, 44, and 64 days old; and convulsive behavior to a convulsant, flurothyl at age 70 days old. Another group of 33-day old offspring whose mothers had received 3 multiple doses of MeHgOH or daily doses of 0 or 4 mg/kg from day 10 to day 12 of gestation were also used for the open-field behavioral study. Prenatal MeHg exposure decreased exploratory behavior as indicated by longer center square latency, lower number of peripheral squares traversed, lower frequency of rearing and grooming lower frequency of urination, and higher frequency of backing, in treated groups in comparison to control groups. Depression in spontaneous locomotor activity was observed in offspring prenatally exposed to MeHg; the effect diminished gradually as the animals grew older. In the flurothyl convulsion behavior test, animals prenatally treated with MeHg demonstrated significantly lower threshold to preliminary clonic convulsion as well as maximal clonic-tonic convulsion; indicating an increase in susceptibility to flurothyl-induced convulsions. The decrease in exploratory behavior and spontaneous locomotor activity with an increase in convulsive susceptibility are not necessarily inconsistent findings and may be due to MeHg affecting 2 independent mechanisms. Behavioral effects can be induced in offspring prenatally exposed to MeHg and can be detected in offspring having no detectable gross congenital malformations.