Prenatal exposure to nicotine impairs protective responses of rat pups to hypoxia in an age-dependent manner

Experiments were carried out on rat pups to investigate the interaction bet ween prenatal exposure to nicotine and postnatal age on protective response s that promote survival during exposure to hypoxia. From days 6 or 7 of ges tation, pregnant rats received either nicotine ( similar to 6 mg of nicotin e tartrate/kg of body weight per day) or vehicle continuously via a 28-day osmotic minipump. On postnatal days 1-2, 5-6 and 10-11, the pups were expos ed either to a single period of hypoxia produced by breathing an anoxic gas mixture (97% N-2 and 3% CO2) and their time to last gasp determined., or t hey were exposed repeatedly to hypoxia and their ability to autoresuscitate from primary apnea determined. Prenatal exposure to nicotine decreased the time to last gasp. but only in the 1-2-day-old animals. The total number o f gasps was., however. increased in this age group due to the effect of nic otine on the gasping pattern. Furthermore. prenatal exposure to nicotine de creased the number of successful autoresuscitations and influenced the card iorespiratory events preceding death in the 1-2- and 5-6-day-old pups but n ot in the 10-11-day-old pups. Thus, our experiments show that prenatal expo sure to nicotine impairs protective responses of rat pups that may sustain life during exposure to hypoxia in an age-dependent manner. (C) 2001 Elsevi er Science BN. All rights reserved.