EFFECTS OF PRENATAL ETHANOL EXPOSURE ON LEARNED PERSISTENCE AND HIPPOCAMPAL NEUROANATOMY IN INFANT, WEANLING AND ADULT-RATS

The present experiment examined whether deficits in learned persistence, previously seen in 15-day-old infant rats prenatally exposed to ethanol, would be present in weanling and adult animals. Three prenatal treatments, EtOH, PAIR-FED, and LAB CHOW, were combined factorially with partial (PRF) or continuous (CRF) reinforcement training followed by extinction, at 21 days or 6 months of age. The results at 21 days were virtually the same as our earlier findings for 15-day-olds: we did not find the higher level of persistence in PRF-trained EtOH pups relative to CRF-trained EtOH pups, which characterizes the partial reinforcement extinction effect (PREE). The EtOH-PRF and EtOH-CRF animals extinguished at about the same rate, both faster than PRF controls. However, when tested as adults, the EtOH-exposed animals showed a normal PREE, with no deficits relative to controls. An analysis of CA1 pyramidal cells in midtemporal hippocampus demonstrated no significant differences in cell density or in CA1 area among the 3 prenatal diet conditions; however, there was a significant reduction in cell density with age for all groups. These results suggest that a developmental delay, unrelated to these neuroanatomical measures, is responsible for the lack of persistence in young rats exposed prenatally to ethanol.