Caudate morphology and behavior of rats exposed to carbon monoxide in utero

Postnatal morphologic damage was found in the caudate nucleus of rats exposed 2 or 3 h to carbon monoxide on gestational day 15. There were gross abnormalities in the form of ecotopic swellings of caudate tissue into the lateral ventricles. The incidence of caudate ectopias was about 20% in rats exposed 2 h as fetuses and 70% from 3 h of exposure. In addition, in the body of the caudate the number of dendritic branches was reduced in Golgi type II neurons. Postnatal behavior of the exposed rats was not significantly altered in a series of behavioral tests of motor function. Growth rate was not retarded. The failure to detect behavioral changes may be due to insensitivity of these tests detecting functional damage or to compensation by the developing brain, resulting in normal function.