The development of daytime rearing behavior in methylazoxymethanol-treated rats: methodological considerations.

The development of daytime rearing behavior was studied in the offspring of pregnant rats which received injections of methylaxymethanol acetate (MAM) or saline during the 15th day of gestation. MAM and control rats were tested at 10, 15, 20, 25, and 30 days of age. The results indicated that the onset of rearing for both groups appeared at approximately 15 days of age, with no significant differences found between sexes. No rearing deficits were seen in MAM rats through 25 days of age despite the fact that these animals sustained greater than a 50% reduction in telencephalic mass. However, at 30 days of age MAM rats reared for significantly longer periods of time during each episode than did their control counterparts, although the actual number of rears did not differ between groups. The results are discussed in terms of neuroplastic events which follow MAM-induced damage and the need for multivariate research when analyzing rearing behavior.