The effects of prenatal methylazoxymethanol acetate (MAM) on holeboard exploration and shuttle avoidance performance in rats.

Forty pregnant rats were given an IP injection of either 0, 14, 22, or 30 mg/kg of MAM on day 15 of gestation. One animal of each sex from each litter was tested between 80 and 90 days of age in a holeboard mounted on a stabilimeter. An additional animal of each sex from each litter was tested between 110 and 120 days of age in a two-way shuttle avoidance task. In the holeboard task, prenatal treatment with MAM resulted in an increased frequency of dipping which was accompanied by an increased number of transitions between holes, rather than stereotypy. Altered patterns of exploratory behavior over the course of the test session were also evident in MAM treated offspring as compared to controls. The 22 mg/kg group tended to show less of a decrease in their activity levels over the course of the session than the other groups. In the shuttle avoidance task, prenatal treatment with MAM resulted in a facilitation of avoidance performance as compared to controls. In addition, increased activity (as measured by intertrial interval crossings) was evident in MAM treated offspring, while escape latencies were equivalent across the groups. However, the pattern of results suggest that the facilitated avoidance performance cannot be accounted for by the increased activity. These results are discussed in terms of various hypothesis which may account for the behavioral deficits shown by MAM treated offspring.