Experimental fetal alcohol syndrome: The effects of prenatal ethanol exposure on reproductive behavior and neuronal expression of the proto-oncogene c-fos

Abstract

Ethanol, the main ingredient in alcohol, is the cause of Fetal Alcohol Syndrome. Although it's mechanisms of actions remain unknown, prenatal exposure to ethanol has been known to produce severe effects on embryogenic development including CNS anomalies, hyperactivity, growth deficits, infant mortality and behavioral abnormalities. This experiment was designed to examine the effects of ETOH exposure in utero on the reproductive behavior and neuronal expression of c-fos in adult male rats. Pregnant rats were divided into three experimental groups and given diets of either 35% ETOH or liquid control or solid food control. Offspring from the ETOH treated group had higher infant morality rates when compared to either the pair-fed or solid food control groups and significantly shorter body lengths on day 1. Results from copulatory tests showed no significant differences in IL, ML and EL between groups for three test sessions. Moreover, the decreases in ML, IL, and EL seen between copulatory tests 1 and 2 denotes a pattern of learning behavior. Therefore,we suggest that ETOH treatment had no significant effects on the sexual learning of the offspring. The immuohistochemical analysis of fos revealed c-fos expression in the NAc, DBB, CPU, and MPOA in animals of all test groups. However, an overall increase in fos levels were found in ETOH teated animals suggesting that prenatal exposure to ETOH elevates the expression of fos in response to stimulation. A significant main effect of diet was seen in the NAc and DBB areas between test groups with a greater number of fos-stained nuclei in the ETOH group. There was also a significant interaction between diet and exposure to female pheromones in the levels of fos expressed in the MPAO. The decreased number of fos-stained nuclei in the ETOH treated animals was related to the ETOH exposure in utero. Exposure to female pheromones caused an increase fos expression in the CPU of solid food diet animals versus controls. Furthermore, fos levels were increased in the ETOH controls as compared to the solid controls. These findings suggest that prenatal exposure to ETOH has little effect on copulatory behavior and no effect on sexual learning. In contrast, a significant effect of ETOH on the neuronal expression of c-fos in selected brain area was observed.