1. @entity8302 ( @entity8302 ) have been shown to generate pacemaker activity in gastrointestinal (GI) muscles. Experiments were performed to characterize the @entity8302 within the @entity235 gastric antrum and to determine the site(s) of pacemaker activity and whether active propagation pathways exist within the thick-walled tunica muscularis of large mammals. 2. Immunohistochemistry and electron microscopy revealed four populations of @entity8302 within the antral muscularis on the basis of anatomical location. Typical @entity8302 were found in the myenteric region of the small intestine (IC-MY). Intramuscular @entity8302 (IC-IM) were intermingled between muscle fibres of circular and longitudinal muscle layers. @entity8302 were also found within septa (IC-SEP) between muscle bundles and along the submucosal surface of the circular muscle layer (IC-SM). @entity8302 were identified in each location by ultrastructural features. 3. Intracellular electrical recordings demonstrated @entity594 -insensitive slow waves throughout the circular muscle layer. Separation of interior and submucosal circular muscle strips from the dominant (myenteric) pacemaker region dramatically slowed frequency but did not block spontaneous slow waves, suggesting that pacemaker cells populate all regions of the circular muscle. 4. Slow waves could be evoked in interior and submucosal circular muscles at rates above normal antral frequency by electrical pacing or by @entity934 (0.3 microM). Active slow wave propagation occurred in all regions of the circular muscle, and propagation velocities were similar in each region. 5. In summary, antral muscles of the @entity235 stomach have pacemaker capability throughout the circular muscle. Normally, a dominant pacemaker near the myenteric plexus drives slow waves that actively propagate throughout the circular layer. Pacemaker activity and the active propagation pathway may occur in networks of @entity8302 that are distributed in the region of the myenteric plexus and throughout the circular muscle layer.

Distribution of pacemaker function through the tunica muscularis of the XXXX gastric antrum.

@entity235 :: ('9615', 'Species') :: ['canine'] @entity8302 :: ('MESH:D007984', 'Disease') :: ['ICC', 'Interstitial cells of Cajal'] @entity934 :: ('MESH:D000109', 'Chemical') :: ['acetylcholine'] @entity594 :: ('MESH:D009543', 'Chemical') :: ['nifedipine']
@entity235 :: (9615,Species) :: ['canine']
