Effects of Nicotine on Chicken Embryonic Development

Abstract

A large proportion of the United States population has been exposed to maternal smoking in utero. Mounting data suggests that nicotine can have a negative impact on neural system development. The goal of this study was to evaluate effects of nicotine exposure on chicken neural system. The early chick embryo is an established model of the first month of embryonic development in mammals. Nicotine (nicotine hydrogen bitartrate) or vehicle (sodium bitartrate monohydrate) solutions were injected in eggs prior to incubation (300ng/ml). Three cohorts of 24 eggs distributed between treatment groups were generated. After injections, eggs were sealed and placed in the incubator. Embryos were harvested on day 5 after injections, evaluated and measured, embedded in paraplast, sectioned, and stained with hematoxylin and eosin for histological analysis. Our data indicates that the nicotine treatment does not affect viability, weight, or length of the embryos. Nonetheless, nicotine notably affects the axial rotation of the embryos (defined as a change in the dorsoventral orientation of the head during development). In this study, altered axial rotation was observed in nicotine treated groups 4 times more often than in controls (p<0.05). Microscopic analysis demonstrated that atypical axial rotation was associated with incomplete closing of the embryonic neural tube in the cervical region, but not in other areas of the tube. Further research is needed to evaluate the exact mechanisms of the developmental insult onto neural system development observed in the present study.