Zebrafish Neuronal Nicotinic Acetylcholine Receptors

Cigarette smoking is a major public health concern. Approximately 20% of pregnant women in the western world continue to smoke during pregnancy despite a number of fetal complications linked with cigarette smoking such as premature birth, low-birth-weight infants, stillbirth and infant death. Nicotine exposure in utero can also result in long-term anatomical, behavioral and cognitive deficits. Nicotine, the main addictive chemical component in cigarette tobacco, is a likely contributor to the adverse outcomes, as fetal brain and spinal cord are primary targets. Nicotine mediates its actions through nicotinic acetylcholine receptors, nAChRs, which are widely distributed throughout the body. To date many disease states have been associated with the nAChRs including Alzheimer’s disease, Parkinson’s disease, schizophrenia, Tourette’s syndrome, epilepsy, and nicotine addiction. Yet, it remains unclear as to how specific nAChRs subtypes function during normal developmental processes and how exposing the fetus to chronic nicotine affects fetal development. The zebrafish (Danio rerio) has shown incredible potential for the examination of events that occur during development. Data presented in this manuscript have resulted in the cloning of two additional zebrafish neuronal nAChR genes. RT-PCR and in situ hybridization studies were used to localize the temporal and spatial RNA expression patterns in developing embryos. Each of the subunits displayed unique expression patterns that were transiently regulated. An antisense oligonucleotide morpholino gene knock down approach was used to determine nAChR function during development. Finally, the treatment of zebrafish embryos and a cell culture system with cholinergic drugs was described. Our results indicate that zebrafish will provide an excellent model for the continued study of the role of cholinergic receptors in neural development.