Electro-acupuncture at ST37 and ST25 induce different effects on colonic motility via the enteric nervous system by affecting excitatory and inhibitory neurons

Neurogastroenterology is defined as neurology of the gastrointestinal tract, liver, gallbladder and pancreas and encompasses control of digestion through the enteric nervous system (ENS), the central nervous system (CNS) and integrative centers in sympathetic ganglia. This Review provides a broad overview of the field of neurogastroenterology, with a focus on the roles of the ENS in the control of the musculature of the gastrointestinal tract and transmucosal fluid movement. Digestion is controlled through the integration of multiple signals from the ENS and CNS; neural signals also pass between distinct gut regions to coordinate digestive activity. Moreover, neural and endocrine control of digestion is closely coordinated. Interestingly, the extent to which the ENS or CNS controls digestion differs considerably along the digestive tract. The importance of the ENS is emphasized by the life-threatening effects of certain ENS neuropathies, including Hirschsprung disease and Chagas disease. Other ENS disorders, such as esophageal achalasia and gastroparesis, cause varying degrees of dysfunction. The neurons in enteric reflex pathways use a wide range of chemical messengers that signal through an even wider range of receptors. These receptors provide many actual and potential targets for modifying digestive function.

The digestive system is innervated through its connections with the central nervous system (CNS) and by the enteric nervous system (ENS) within the wall of the gastrointestinal tract. The ENS works in concert with CNS reflex and command centers and with neural pathways that pass through sympathetic ganglia to control digestive function. There is bidirectional information flow between the ENS and CNS and between the ENS and sympathetic prevertebral ganglia.The ENS in human contains 200-600 million neurons, distributed in many thousands of small ganglia, the great majority of which are found in two plexuses, the myenteric and submucosal plexuses. The myenteric plexus forms a continuous network that extends from the upper esophagus to the internal anal sphincter. Submucosal ganglia and connecting fiber bundles form plexuses in the small and large intestines, but not in the stomach and esophagus. The connections between the ENS and CNS are carried by the vagus and pelvic nerves and sympathetic pathways. Neurons also project from the ENS to prevertebral ganglia, the gallbladder, pancreas and trachea.The relative roles of the ENS and CNS differ considerably along the digestive tract. Movements of the striated muscle esophagus are determined by neural pattern generators in the CNS. Likewise the CNS has a major role in monitoring the state of the stomach and, in turn, controlling its contractile activity and acid secretion, through vago-vagal reflexes. In contrast, the ENS in the small intestine and colon contains full reflex circuits, including sensory neurons, interneurons and several classes of motor neuron, through which muscle activity, transmucosal fluid fluxes, local blood flow and other functions are controlled. The CNS has control of defecation, via the defecation centers in the lumbosacral spinal cord. The importance of the ENS is emphasized by the life-threatening effects of some ENS neuropathies. By contrast, removal of vagal or sympathetic connections with the gastrointestinal tract has minor effects on GI function. Voluntary control of defecation is exerted through pelvic connections, but cutting these connections is not life-threatening and other functions are little affected.

Traditionally, acupuncture is embedded in naturalistic theories that are compatible with Confucianism and Taoism. Such ideas as yin-yang, qi, dampness, and wind represent East Asian conceptual frameworks that emphasize the reliability of ordinary, human sensory awareness. Many physicians who practice acupuncture reject such prescientific notions. Numerous randomized, controlled trials and more than 25 systematic reviews and meta-analyses have evaluated the clinical efficacy of acupuncture. Evidence from these trials indicates that acupuncture is effective for emesis developing after surgery or chemotherapy in adults and for nausea associated with pregnancy. Good evidence exists that acupuncture is also effective for relieving dental pain. For such conditions as chronic pain, back pain, and headache, the data are equivocal or contradictory. Clinical research on acupuncture poses unique methodologic challenges. Properly performed acupuncture seems to be a safe procedure. Basic-science research provides evidence that begins to offer plausible mechanisms for the presumed physiologic effects of acupuncture. Multiple research approaches have shown that acupuncture activates endogenous opioid mechanisms. Recent data, obtained by using functional magnetic resonance imaging, suggest that acupuncture has regionally specific, quantifiable effects on relevant brain structures. Acupuncture may stimulate gene expression of neuropeptides. The training and provision of acupuncture care in the United States are rapidly expanding.