Crucial role of the postnatal maternal environment in the expression of prenatal stress effects in the male rats.
Methodological and conceptual problems common in prenatal stress experiments were analyzed, and an experiment incorporating solutions to those problems were designed and executed. Rats were prenatally stressed or served as controls and then were cross-fostered within or between treatment groups. In adulthood, one male from each litter was tested over 20 trials in an open-field box and then tested over 20 successive discrimination reversals in a T-maze. A T-factor analysis was performed on each of the two sets of observations, and factors scores were subjected to elevational analyses. Major hypotheses generated from the results are the following: (a) Male rats subjected to prenatal stress acquire emotional reactivity levels in adulthood that are either elevated or reduced depending on the postnatal maternal environment. (b) Male rats subjected to prenatal stress acquire reversal learning sets in adulthood with a rapidity that parallels and indeed is produced by the pattern of emotional reactivity reflected in the above a and as mediated by cognitive processes. (c) T-factor analysis of trials is required in order to avoid construct validity problems as well as internal validity problems, both brought about by the confounding of trial variables, and in addition, it may generate valuable hypotheses giving further meaning to the dependent variables under observation.