Ontogeny of second messenger systems

Second messengers provide a direct connection between signaling molecules such as neurotransmitters, cytokines, and growth factors and changes in gene expression that are ultimately responsible for the proliferation, differentiation, and maturation of nerve cells. This interaction of signaling molecules through second messenger systems might direct the development of the nervous system. Numerous studies have suggested a role of cell signaling during different stages of nervous system development, thereby enhancing the action of extracellular signals. These cell-signaling pathways are highly interactive and maintain a modulatory interaction with each other via a complex network of second messenger systems. Our increasing understanding of these second messengers mediated cellular signaling systems at specific ontogenetic stages suggests that certain developmental neurotoxicants may exert their toxicity by interfering with these processes. By understanding the pathways of toxicity induced by a developmental neurotoxicant and correlating such mechanisms of toxicity with certain second messenger pathways, it is possible to construct experimentally viable hypotheses on potential mechanisms of neurotoxic damage.