EFFECTS OF PRENATAL EXPOSURE TO LOW CONCENTRATIONS OF CARBON-MONOXIDEON SEXUAL-BEHAVIOR AND MESOLIMBIC DOPAMINERGIC FUNCTION IN RAT OFFSPRING

1 Inhalation of low concentrations of carbon monoxide (CO) by pregnant rats (75 and 150 p.p.m. from day 0 to day 20 of gestation) leads to c hanges in mesolimbic dopaminergic transmission associated with an impa irment of sexual behaviour in male offspring. 2 Eighty day old males e xposed in utero to CO (150 p.p.m.) exhibited a significant increase in mount/intromission latency as well as a significant decrease in mount /intromission frequency. A significant decrease in ejaculation frequen cy was also found in CO (150 p.p.m.)-exposed animals. 3 The acute admi nistration of amphetamine, at a dose (0.5 mg kg(-1) s.c.) stimulating copulatory activity in control rats, failed to reduce mount/intromissi on latency and did not increase mount frequency in 80-day offspring ex posed to CO (150 p.p.m.) during gestation. 4 These behavioural alterat ions were paralleled by neurochemical changes (in vivo microdialysis) showing that prenatal CO exposure, at concentrations (150 p.p.m.) that did not affect basal extracellular levels of dopamine in the nucleus accumbens, blunted the amphetamine (0.5 mg kg(-1) s.c.)-induced increa se in dopamine release in 80-day old male rats. 5 No significant chang es in either behavioural or neurochemical parameters were observed in 10-month old rats exposed prenatally to CO. 6 Since the alterations in sexual behaviour and dopaminergic transmission have been produced by prenatal exposure to CO levels resulting in maternal blood carboxyhaem oglobin concentrations equivalent to those maintained by human cigaret te smokers, the present data further point out the large risk that the smoking mother poses for her offspring.