The Effect of Local Anesthetics on Neurulation of Early Chick Embryos

ABSTRACT

Chick embryos have been used widely as model systems for studies in experimental embryology and teratology. Especially early chick embryos are very useful for studies of neural tube defects. Local anesthetics such as lidocaine, tetracaine and ketamine are known to inhibit the formation of microfilaments and cause neural tube defects. We made a try to figure out the effect of local anesthetics on neurulation in early chick embryo, which is stage 8 by Hamburger & Hamiliton classification. After 6~9 hours incubation in media treated with above local anesthetics, we observed the effects of these agents by LM and EM. Stage 8 chick embryos responded to local anesthetics in a dose related manner. Tetracaine showed most potent effects. Neural folds failed to make a contact, so the neural tube was left open. In high dosage, the case of no growth or little growth of embryo was also observed. On scanning electron microscopic examination, the surface of neuroepithelium was flattened in embryos treated with ketamines. On transmission electron microscopic examination. neuroepithelium of embryos cultured in ketamine showed the decrease of microfilaments and less conspicuous feature of mitochondria and rough ER(endoplasmic reticulum)'s.