The effects of vitamin A excess administered during the mid‐fetal period on learning and development in rat offspring

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Abstract
Pregnant rats were administered a teratogenic dose of vitamin A excess on Days 17 and 18 of gestation. Intubation controls received the vehicle alone and nontreated mothers were left undisturbed. All groups were fostered to other nontreated mothers at birth. During adulthood, offspring were lever‐trained to obtain a water reward on an intermittent reinforcement schedule and on an S+, S− auditory discrimination. Unlike animals treated with vitamin A excess on Days 14 and 15 of gestation, these animals revealed no retardation in growth and development nor in brain size. Throughout the VI‐40 sessions and the S+ trials of discrimination training, the vitamin A animals had consistently slower rates of response compared to the controls. However, they did not evidence any impaired learning ability; like the nontreated, they extinguished S− responding, acquired long S− latencies, and maintained short S+ latencies. Possibly, the treatment may have produced a subtle motor deficit affecting fine motor coordination.