Cerebral Signal Transduction: From First to Fourth Messengers

Since the pioneering discovery of cyclic AMP four decades ago, a multitude of signaling pathways have been uncovered in which an extracellular signal (first messenger) impacts the cell surface, thereby triggering a cascade that ultimately acts on the cell nucleus. In each cascade the first messenger gives rise to the appearance of a second messenger such as cyclic AMP, cyclic GMP, or diacylglycerol, which in turn triggers a third messenger, a fourth messenger, and so forth. Many advances in...