Functional coupling of neurotransmitters with second messengers during cleavage divisions: Facts and hypotheses

Current data on the role of classical neurotransmitters as multiple and mul tifunctional regulators of early embryogenesis are reviewed. It is shown th at these developmental regulators are coupled with second messengers. Pecul iarities of this prenervous coupling emphasized and are used as the basis f or discussing the problem of the evolutionary origin of cell regulatory sys tems.