Postnatal behavior in Hatano high- and low-avoidance rats following prenatal exposure to low-dose methylazoxymethanol

The hypothesis that genetic factors influence behavioral effects was tested in rats exposed prenatally to methylazoxymethanol (MAM). We examined wheth er baseline behavior is an important factor influencing behavioral effects, and whether a behaviorally selected strain was useful for study of neurobe havioral teratology. Pregnant high- and low-avoidance animals (HAAs and LAA s) of the Hatano strain, selectively bred for high and low shuttlebox avoid ance responses, respectively, were given an IP injection of a low dose of M AM (15 mg/kg) on day 14 of gestation. The offspring of these animals were s ubjected to behavioral tests for locomotor activity (running-wheel and open -field tests) and learning ability (Biel maze and shuttlebox avoidance test s). There were no significant effects of MAM on running-wheel activity or s huttlebox avoidance learning, whereas the number of errors in the Biel maze was increased in the MAM offspring of both strains. interestingly, open-fi eld activity of the MAM offspring was markedly decreased in LAAs but not in HAAs. Therefore, an additional experiment was performed to determine plasm a levels of ACTH and corticosterone following open-field exposure, When com pared to control offspring of the respective strains, plasma levels of ACTH and corticosterone were not altered by prenatal MAM treatment in LAAs. Ins tead, the MAM offspring in HAAs exhibited decreased ACTH levels in absence of behavioral alterations. These results demonstrated that prenatal exposur e to low doses of MAM may alter postnatal behavior and endocrine response o f the offspring, although to a differing degree in HAAs and LAAs. Our obser vations suggested that behaviorally selected strains are sensitive to neuro behavioral teratogens such as MAM. (C) 2000 Elsevier Science Inc. All right s reserved.