Neuronal control of the pyloric sphincter of the guinea‐pig

Abstract

The pyloric sphincter (PS) controls gastric emptying and prevents the reflux of duodenal content into the stomach. Neuronal pathways and reflexes controlling the guinea-pig PS were physiologically investigated in isolated preparations. Simultaneous intracellular or extracellular and tension recordings from PS circular muscle with electrical and stretch stimulation were used. Electrical stimulation evoked an initial small contraction followed by a relaxation with a corresponding inhibitory junction potential (IJP) then a second large contraction with a corresponding excitatory junction potential (EJP). Hyoscine (1 micromol L-1) blocked the first contraction, and reduced the second contraction and EJP by 52.5% and 61%, respectively. These responses were further reduced by the NK2 antagonist, MEN10627 (1 micromol L-1), and the NK1 antagonist, SR140333 (1 micromol L-1). N-nitro-L-arginine (100 micro;mol L-1) and apamin (0.5 micromol L-1) blocked the relaxation and the IJP. Duodenal electrical stimulation evoked an EJP, whereas antral stimulation evoked an IJP followed by a small EJP. All were blocked by hexamethonium (100 micromol L-1). Duodenal stretch evoked tetrodotoxin-sensitive reflex contractions and membrane depolarization with action potentials in the PS. Thus, PS enteric motor neurones receive inputs from the duodenum and the stomach. There are stretch-sensitive ascending excitatory reflex pathways from the duodenum to the PS.

Quantification of the Effects of the Volume and Viscosity of Gastric Contents on Antral and Fundic Activity in the Rat Stomach Maintained Ex Vivo

“…Hence, in our preparation, prepyloric mechanoreceptors responding to high circumferential tension or hoop stress [65,66] may promote sphincter constriction. This hypothesis is supported by work showing that circumferential stretch of the distal antrum evokes transient phasic contractions in the pyloric sphincter [67]. Thus, although the vagus nerve may be necessary for the efficient function of the pyloric sphincter [68], local myogenic [45] or enteric neural activity [69] may augment the role of the pyloric sphincter as the 'the keeper of the gate' [70].…”

Lack of pyloric interstitial cells of Cajal explains distinct peristaltic motor patterns in stomach and small intestine

“…The high density of ICC-IM and their close innervation suggest a regulatory function for ICC-IM in pyloric innervation (54,57). Both extrinsic and intrinsic nerves supply the pylorus where they function to regulate gastric emptying and prevent reflux of duodenal content (59). The enteric nerves can also provide gastroduodenal coordination; an example is the orchestration of the migrating myoelectric complex (MMC) (46) that can propagate from the stomach into the duodenum.…”

“…It is clear that the pylorus does not have a primary pacemaker system in connection with the networks of ICC-AP in stomach and duodenum. Pyloric phasic contractile activities (52) rely on 1) excitation of the pyloric muscle cells and ICC-IM by efferent nerve supply specific to the pylorus (59) or 2) propagation of action potentials from the gastric or duodenal Fig. 9.…”

Intrinsic neuronal control of the pyloric sphincter of the lamb

“…There is also evidence that duodenal local nerve fibres may modulate the PS in monogastric species; neuronal feedback mechanisms triggered by the luminal contents in the duodenum seem to be very important for PS motility (Yuan et al, 2001;Lindeströ m and Ekblad, 2002;Treacy et al, 1992;Allescher et al, 1989).…”

“…The pylorus represents a short section of the gastroduodenal junction whose lumen contains a rounded thickness of the wall termed pyloric torus. The pyloric region has been the subject of numerous investigations in man (Torgesen, 1942;Fisher and Cohen, 1973;Ramkumar and Schulze, 2005), dogs (Torgesen, 1942;Allescher et al, 1988;Daniel et al, 1989;Mochiki et al, 2001), guinea-pigs (Cai and Gabella, 1984;Iino, 2000;Yuan et al, 2001), rats (Kressel et al, 1994;Lindeströ m and Ekblad, 2002), ruminants (Ruckebusch and Malbert, 1985;Malbert and Ruckebusch, 1991;Plaza et al, 1996), pigs (Torgesen, 1942;Treacy et al, 1992), and several other species, such as rabbits, cats, and horses (Torgesen, 1942).…”