Gestational exposure to nicotine in drinking water: teratogenic effects and methodological issues

Abstract

Individual differences in nicotine effects lead to questions about appropriate experimental procedures for prenatal nicotine exposure in rodent models. The objective of this study was to develop a method for gestational studies in rats based on oral nicotine exposure, and to evaluate the neurodevelopmental effects. Female Lister hooded rats were exposed to nicotine solutions both before and during pregnancy. These female rats were divided into groups consuming solutions of different concentrations such that animals that initially consumed the solutions most readily were exposed to progressively higher concentrations. Offspring of these female rats were evaluated in a test battery measuring maturational and developmental milestones. Female rats ingested nicotine solutions at levels that provided blood nicotine concentrations of 10-60 ng/ml, at daily dose levels of 2.9-6.2 mg/kg. Solutions with concentrations below 0.06 mg/ml were well tolerated with some moderate adverse effects at the highest dose. Concentrations above 0.08 mg/ml led to a large drop in fluid consumption and in body weight. Strong teratogenic effects of prenatal nicotine exposure were observed at concentrations above 0.04 mg/ml, including developmental and maturational delays shown by measures of pinnae detachment, fur appearance, incisor eruption, eye opening and righting reflex. Negative geotaxis, grip strength and weight gain were impaired and postnatal mortality was increased. This study design provides a model for the impact of prenatal exposure to nicotine at blood levels comparable with those in medium and heavy smokers. There were marked developmental and behavioural deficits induced in the offspring of nicotine-exposed female rats.

Figure 1

Decreased body weight (A) and delayed maturation (B-D) in offspring whose mothers were exposed to different concentrations of nicotine in tap water as the only source of fluid for four weeks before mating and during pregnancy. Data are shown as means + SEM. Litter (Con=12, 0.04=5, 0.06=5, 0.08=4) was used as the unit for analyses. Post hoc Least Significance Difference Test results significant at least at p<0.05 are marked as follows: * vs. Con, + vs. 0.04 mg/ml, § vs. 0.06 mg/ml group.

Figure 2

Impairment of motor coordination (A, B) and muscle strength (C) in offspring whose mothers were exposed to different concentrations of nicotine in tap water as the only source of fluid for four weeks before mating and during pregnancy. There was no impact of prenatal nicotine exposure on the offspring’s locomotor activity on PND 19 (D). Data are shown as means + SEM. Litter (Con=12, 0.04=5, 0.06=5, 0.08=4) was used as the unit for analyses. Post hoc Least Significance Difference Test results significant at least at p<0.05 are marked as follows: * vs. Con, + vs. 0.04 mg/ml, § vs. 0.06 mg/ml group.