ABSTRACT
A large number of neuropeptides have been found in the intestine. In mammals, these neuropeptides are contained in nervous structures and presumably act as neurotransmitters and neuromodulators. The neurokinin substance P (SP) and its homologue neurokinin A are well represented and have been shown to participate in the regulation of gastrointestinal functions by the intermediacy of specific receptors. The pharmacological effect and the possible physiological role of neurokinins on the intestine have mainly been studied in the guinea pig. In vitro, the guinea pig ileum has been used extensively by practically all investigators in the field of substance P. The three neurokinin receptors are all present in the tissue and contribute to activation of intestinal movements. Neurokinin receptors are present in the colon of various species, including men. SP and related neurokinins may be involved in the pathogenesis of colonic diseases such as the Hirschsprung’s disease and other diseases.
