Enhanced acquisition and retention of passive avoidance behaviour in adult rats given a single transuterine ACTH injection while fetuses.

The long-term effects of a single ACTH injection administered to fetuses by transuterine way, on the ability to learn and retain a noxious significance were studied. The investigation was carried out on 115 adult rats of either sex. During the experiment the authors examined the range of inborn avoidance behaviour (light avoidance), as well as the ability to develop and retain a passive avoidance response. The ACTH-treated group did not present a significant difference of light avoidance behaviour as compared to controls, showing nevertheless a significantly higher learned passive avoidance and a delayed extinction of the noxious significance. The role of pituitary-adrenal hormones in the mechanism of avoidance behaviour during ontogenetic development is discussed.