FIGURE 37-1 The neuronal network that initiates and generates the peristaltic response. Mucosal stimulation leads to release of serotonin by enterochromaffin cells (8), which excites the intrinsic primary afferent neuron (1), which then communicates with ascending (2) and descending (3) interneurons in the local reflex pathways. The reflex results in contraction at the oral end via the excitatory motor neuron (6) and aboral relaxation via the inhibitory motor neuron (5). The migratory myoelectric complex (see text) is shown here as being conducted by a different chain of interneurons (4). Another intrinsic primary afferent neuron with its cell body in the submucosa also is shown (7). MP, myenteric plexus; CM, circular muscle; LM, longitudinal muscle; SM, submucosa; Muc, mucosa. (Adapted from Kunze and Furness, 1999, with permission.)
dopamine receptor antagonists are effective as prokinetic agents; they have the additional advantage of relieving nausea and vomiting by antagonism of dopamine receptors in the chemoreceptor trigger zone (see below). Examples of such agents are metoclopramide and domperidone.
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