We work with several experimental systems in which cyclic GMP regulates physiologic and metabolic events. In some studies, we have focused on specific populations of neurons in the mammalian central and peripheral nervous system, where we are beginning to learn how cyclic GMP functions in cell-cell communication. In other studies, we have focused on invertebrate neuronal preparations, where cyclic GMP regulates neural development and the pattern-generating networks that control gastric and cardiac physiology. For additional research, visit the Curriculum in Neurobiology home page . However, over the last several years, much of our primary research effort has focused on the epithelial lining of the mammalian intestine, where cyclic GMP controls the luminal secretion of ions and water.
Water plays a vital physiological role in the intestine.
It serves as the medium in which food particles are suspended for efficient transport along the length of the intestine, and it provides the aqueous environment required for the proper action of digestive enzymes. Once formed, mucus lubricates the lining of the GI tract, protecting it from mechanical damage and the harmful effects of stomach acid and bacterial or viral pathogens. It is clear that a delicate balance must be maintained between the pathway that controls mucin secretion and the pathway that controls water secretion. If there is underproduction of water, as occurs in cystic fibrosis, the mucus that forms is too thick, and it clogs up the system, leading to intestinal blockage. If there is overproduction of water, as occurs in diseases like cholera and toxic E. coli infections, the excessive amount of fluid in the intestine overwhelms the absorptive capacity of the mucus, and the result is diarrhea.