The early chick embryo as a model to evaluate cardiovascular effects of adrenaline and nicotine

During the early stages of development, chick embryos offer a good model for vascular and circulatory studies. The present experiments were carried out with nicotine and adrenaline as validation substances, to test whether this system can be applied to evaluate functional cardiovascular effects. Nicotine was injected into the yolk before incubation and administered topically on different days of incubation. Adrenaline was injected intravascularly to evaluate functional effects (heart rate and heart arrhythmia). Mortality rates following nicotine and adrenaline application were determined. An injection of nicotine prior to incubation resulted in a dose-related increase in undeveloped chick embryos, and the topical application led to hyperaemia and haemorrhages. The body weight of the embryos was reduced due to the repeated nicotine application. After iv injection of adrenaline, heart rate increase and the occurrence of heart arrhythmia showed dose-response effects and the mortality rate was three-fold higher as compared with the controls. These results show that, following the application of adrenaline and nicotine, effects on the early chick embryo are similar to those seen in other test systems. In addition to its use in toxicology, this model is suitable for the evaluation of functional cardiovascular effects. The system does not require living animals, and uses stages of development during which the nervous system is still immature.