Purpose The Surgeon General's 2001 report entitled “Women and Smoking” found that between 12% (from studies of birth certificates) to 22% (according to surveys) of U.S. mothers smoked while pregnant. Many studies have demonstrated that infants prenatally exposed to nicotine show more signs of stress, hyper-excitability, and addictability, as well as oppositional, aggressive and overactive behavior. Nicotine, a predominant substance found in cigarettes, also functions as a neurotransmitter at Nicotinic Acetycholine Receptors (nAChRs). It has been demonstrated that chronic nicotine exposure in mice leads to down-regulation of existing nAChRs. Such findings suggest that Prenatal Nicotine Exposure (PNE) may affect the development of nAChR-regulated pathways, thereby producing the cognitive, emotional, and behavioral abnormalities found in offspring prenatally exposed to nicotine.
Methods During gestation, 12 female dams were fed a nicotine/saccharine solution, 12 other female dams were fed a nicotine/water solution, for a total of 24 dams. A power analysis was used to identify the minimum number of animals needed to avoid a Type II error. A sample size of at least 10 would provide a 90% power for significance determinations. There were three arms to the study. 1) Locomotor Activity Measurement- Quantified via Opto-varimex were the following behaviors: horizontal activity, total distance traveled, ambulatory time, rest time, vertical activity, stereotypic activity, and time spent in stereotypic activity. 2) Learned Helplessness- Mice were conditioned to associate a tone with a subsequent foot shock. In a novel, environment mice were again exposed to the tone without shock. Mice were observed for freezing behavior as a measure of learning. 3) Place Preference- Mice were conditioned with either a saline or cocaine injection in two distinct rooms and isolated in each room, respectively. Mice were later allowed free access to either room. Time spent in the drug-paired side was compared to time spent in the saline-paired side.
Results PNE mice were shown to be more hyperactive, displayed greater learning of painful stimuli, and exhibited enhanced addictability compared to non-PNE mice.
Conclusions The negative and numerous effects of inhaling smoke have been generally known for sometime. Our research shows that aside from the negative effects of second-hand smoke exposure, there are negative effects from second-hand nicotine exposure, as well. A greater effort must be made by proponents of public health to prevent women from smoking while pregnant.
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