Effect of prenatal alcohol exposure on midsagittal commissure size in rats

Background: Fetal alcohol exposure in humans can cause a variety of brain a nd behavioral abnormalities. The brain abnormalities include defects in the corpus callosum that range from total absence (agenesis) to reduction in s ize or thickness. Determination of the critical alcohol level or time perio d of exposure to produce these effects is difficult because of the lack of control of possible mitigating factors. Methods: The present study was undertaken to examine possible relationships between midsagittal corpus callosum dimensions and prenatal alcohol level as measured by blood alcohol concentration, as well as prenatal period of e xposure as measured by first- or second- or first- plus second trimester eq uivalents in a rat model. In addition to the corpus callosum, the hippocamp al and anterior commissures were also examined. Pregnant mothers were given a single daily dose of alcohol by intragastric gavage; four different dose s were tested in different mothers. Peak blood alcohol concentration was de termined at one of four hourly intervals thereafter. Control pregnant mothe rs were pairfed to individual alcohol treated mothers and handled according ly, but no alcohol was given. Other controls consisted of normal, untreated pregnant mothers. Results: The results show all measures of corpus callosum and anterior comm issure were not affected by any dose of alcohol during any time period. How ever, higher BAC levels during prolonged periods of alcohol exposure were a ssociated with reduced size of the hippocampal commissure. Conclusions: The results suggest that additional experimental factors not i ncluded in the present study ave responsible for the effects observed in hu mans. Teratology 63:15-22, 2001. (C) 2001 Wiley-Liss, inc.