The Intrinsic Reflex Circuitry of the Inflamed Colon

In 1899, Bayliss and Starling determined that the innervation of the intestines differs from that of other organs. They found that local neuronal networks are capable of generating reflex responses without the involvement of the central nervous system (Bayliss and Starling 1899). Once this unique feature of the enteric nervous system (ENS) was identified, it took roughly a century for enteric neurobiologists to accomplish the task of being able to identify the components of this "intrinsic neural mechanism", including intrinsic primary afferent neuron, ascending and descending interneuron, and excitatory and inhibitory motor neurons (Bayliss and Starling 1899). Once this was possible, we and others began to investigate the intrinsic circuitry of the colon and ileum to systematically determine the cellular mechanisms that explain the changes in motility and secretion that occur in intestinal inflammation. We wanted to establish what changes occur in the enteric neural circuitry, where they occur, the mechanisms responsible for these changes, and how these changes in the neural circuitry impact intestinal function.