The intrinsic innervation of the human alimentary tract and its relation to function.

Abstract

SUMMARY The intrinsic innervation of the human gut has been studied in strips of circular and longitudinal muscle removed at operation. Studies using drugs to stimulate the nerves within strips of human gut muscles have indicated marked regional differences in innervation (Bennett and Whitney, 1966a;Bennett, 1968;Bennett, 1970). It is of particular interest that these differences seem to correlate with regional functions and the dependence on extrinsic innervation. The drugs used were ganglion stimulants such as nicotine, which are thought to cause contraction of gut muscle by exciting cholinergic nerves and relaxation by stimulating adrenergic nerves. In brief, the experiments have indicated weak cholinergic and adrenergic intrinsic activity in human stomach (Bennett and Whitney, 1966b), suggesting a dependence of gastric motility on extrinsic (vagal) innervation. In the highly motile jejunum the intrinsic cholinergic activity overshadows the adrenergic activity (Whitney, 1965), whereas the reverse is true in the less motile colon Parks, 1963a, 1966;Bucknell and Whitney, 1964), and the terminal ileum shows an intermediate picture (Bennett, 1965). The importance of these implications makes it necessary to verify and extend the results by different methods.Since drugs might not stimulate all the nerves present, and they may produce effects unrelated to nerve activation, experiments have been made with

Metabolites of Arachidonic Acid Formed by Human Gastrointestinal Tissues and Their Actions on the Muscle Layers

“…Similar differences in sensitivity occur with PGF2,, in the normal human ileum and colon in vivo (Cummings, Newman, Misiewicz, MiltonThompson & Billings, 1973;Hunt, Dilawari & Misiewicz, 1975), and with PGE2, PGF2a or PGI2 in rat isolated stomach and colon (Gilmore, Vane & Wyllie, 1968;Omini, Moncada & Vane, 1977). Various other gradients occur in the human gut, such as biochemical and electrical activities (Alvarez, 1948), the muscle response to gastrin (Waller & Misiewicz, 1979) and innervation (Bennett & Stockley, 1975).…”

The effects of electrical field stimulation and tetrodotoxin on ion transport by the isolated rabbit ileum.

“…The responses we measure may be caused by the interaction of several substances because the intestine contains fibers that are cholinergic, adrenergic, nonadrenergic inhibitory, and noncholinergic excitatory (17). The potential sites of action of tetrodotoxin are also increased by the presence in the small intestine of 12 endocrine cell types (18), for tetrodotoxin may affect not only nerve fibers but paracrine cells, because depolarizing currents cause action potentials similar to those of sympathetic neurons in a wide variety of cells capable of secreting amines or polypeptides (APUD cells) (14).…”

The Contribution of Prostaglandins in the Muscle of Human Isolated Small Intestine to Neurogenic Responses

“…Prostaglandins appear to facilitate responses mediated by cholinergic nerves in the longitudinal muscle of guinea-pig isolated ileum (for discussion, see Bennett, Eley & Stockley, 1975b As reported previously, the responses of human ileal strips to electrical stimulation are complex (Bennett & Stockley, 1975 Electrical stimulation (20 s trains; 1 ms pulses; 16 V/cm) produced various combinations of relaxations and initial-and after-contractions. n is the number of strips that produced a particular type of response at each frequency.…”

“…This probably explains the reduction of nerve-mediated relaxations (both were restored by 5-HT), the enhanced contractions to ACh (Bennett & Stockley, 1975) Milton-Thompson & Billings (1973) found that intravenous prostaglandin F2a in man inhibited intraluminal pressure changes; perhaps it caused a maintained increase in muscle tone but increased the baseline intraluminal pressure only transiently because the intestine is an open tube. Superimposed pressure waves would therefore be smaller.…”