PRENATAL METHYL MERCURY EXPOSURE .2. ALTERATIONS IN LEARNING AND PSYCHOTROPIC-DRUG SENSITIVITY IN ADULT OFFSPRING

  • 1 January 1982
    • journal article
    • research article
    • Vol. 4  (3) , 377-382
Abstract
Male Long-Evans rats exposed in utero to 5 or 8 mg/kg of methyl mercury administered as a single dose on either days 8 or 15 of gestation were tested as adults in 2 operant tasks. In 1 task the animals were trained on 2-way avoidance to a criterion of 10 consecutive avoidances. Following acquisition the animals were extinguished and 24 h later re-trained to the previous criterion. Animals treated with 8 mg/kg on day 8 of gestation required significantly more trials to reach criterion during reacquisition than controls. Rats treated on day 15 with either 5 or 8 mg/kg took significantly more trials to reach criterion during acquisition than controls, and of the 8 mg/kg group 55% failed to reach criterion. Rats treated with 8 mg/kg of mercury on day 8 of gestation acquired a DRL-[differential reinforcement of low rates]-10 s task at the same rate as controls. When challenged with d-amphetamine the treated animals were less disrupted at the higher dose (1.0 mg/kg) than controls, suggesting a shift in the dose response curve for this psychoactive drug. Activity measures taken simultaneously with the DRL session confirmed this shift in amphetamine effect. A single prenatal exposure to methyl mercury apparently can affect learning and drug sensitivity of the adult animal. Mercury exposure in late gestation has more deleterious consequences on learning ability than early exposure.

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