Effects of early postnatal exposure to low concentrations of carbon monoxide on cognitive functions in rats

Male Wistar rats were exposed to 75 and 150 ppm of carbon monoxide (CO) fro m day 1 after birth until postnatal day 10 and their cognitive functions we re evaluated at 3 and 18 months of age. The results show that early postnat al exposure to CO does not affect the acquisition and reacquisition of an a ctive avoidance task in both adult and aged rats. Conversely, our previous findings indicate that prenatal exposure to CO (75 and 150 ppm), resulting in maternal blood carboxyhaemoglobin concentrations equivalent to those fou nd in human cigarette smokers, induces long-lasting learning and memory def icits. These findings suggest that neurofunctional sequelae of prenatal CO exposure are notably different from those occurring in response to early po stnatal exposure and that the vulnerability of the developing brain to prol onged, relatively mild, decrease in oxygen availability induced by CO criti cally depends on the particular period of developmental exposure. (C) 1999 Academic Press.