NEUROBEHAVIORAL CHANGES PRODUCED IN RATS BY PRENATAL EXPOSURE TO CARBON-MONOXIDE

Wistar female rats were exposed to relatively mild concentrations of c arbon monoxide (75 and 150 ppm) from day 0 to day 20 of pregnancy. The results show that prenatal exposure to CO (150 ppm) produced a signif icant reduction in the minimum frequency of ultrasonic calls emitted b y rat pups removed from their nest. Moreover, a significant decrease i n the responsiveness (rate of calling) to a challenge dose of diazepam (0.25 mg/kg) was found in male pups exposed to CO (150 ppm) during ge station. Prenatal CO (75 and 150 ppm) did not significantly affect loc omotor activity or D-amphetamine-induced hyperactivity in both 14- and 21-day-old animals. Furthermore, adult male rats exposed to this chem ical (150 ppm) during gestation exhibited significant alterations in t he acquisition of an active avoidance task. CO-induced learning disrup tion does not seem to be linked to changes in the emotionality of anim als. These findings suggest that gestational exposure to CO induces in rat offspring both short- and long-term behavioral changes characteri zed by altered ontogeny of emotional responsiveness to environmental c hallenges and by learning impairment.