Effects of postnatal exposure to cocaine on the development of the rat corpus callosum.

We investigated the effects of cocaine on the development of the corpus callosum in rats. From postnatal days 1 (P1) to 10 (birth = P0), cocaine (10 mg/kg) was subcutaneously injected in the pups, and saline, at the same volume, was administered to control pups. The animals were sacrificed at 110 days of age and a midsagittal section of the callosum was obtained. Morphometric measurement of the corpus callosum was performed in this section. In the control group, but not in the cocaine group, males had larger callosa than females. The cocaine treatment significantly decreased the total callosal area in male rats. These findings indicate that early postnatal cocaine abolishes the sexual differentiation of the corpus callosum.