Impaired alternation test performance in adult rats following prenatal alcohol exposure.

The effects of prenatal exposure to ethanol on an alternation test were examined in adult Long Evans rats from three prenatal treatment groups: prenatal alcohol exposed (35% ethanol-derived calories, 35% EDC), nutritional control (0% ethanol-derived calories, 0% EDC) or standard control (lab chow, LC). Subjects were trained to alternate presses on levers to the left and right of a center food trough. Prenatal treatment did not affect the acquisition of this spatial alternation task. However, during the asymptotic performance phase of the task, subjects prenatally exposed to alcohol received fewer rewards and made more errors compared to the two control groups, which did not differ from each other. Even when test sessions were limited to 10 min, performance deficits in the 35% EDC group persisted. When visual cues were made available above the correct bar in a second experiment, performance deficits in alcohol-exposed subjects were no longer apparent. Marked sex differences were also noted in this task: males received more reinforcements, but also made more errors. Prenatal alcohol exposure may disrupt the normal development of behavioral laterality subserving position preferences, and this disruption may partly explain why performance of some spatial tasks is particularly sensitive to the effects of prenatal alcohol exposure.