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Slow waves are known to originate orally in the stomach and to propagate toward the antrum, but the exact location of the pacemaker and the precise pattern of propagation have not yet been studied. Using assemblies of 240 extracellular electrodes, simultaneous recordings of electrical activity were made on the fundus, corpus, and antrum in open abdominal anesthetized dogs. The signals were analyzed off-line, pathways of slow wave propagation were reconstructed, and slow wave velocities and amplitudes were measured. The gastric pacemaker is located in the upper part of the fundus, along the greater curvature. Extracellularly recorded slow waves in the pacemaker area exhibited large amplitudes (1.8 [+ or -] 1.0 mV) and rapid velocities (1.5 [+ or -] 0.9 cm/s), whereas propagation in the remainder of the fundus and in the corpus was slow (0.5 [+ or -] 0.2 cm/s) with low-amplitude waveforms (0.8 [+ or -] 0.5 mV). In the antrum, slow wave propagation was fast (1.5 [+ or -] 0.6 cm/s) with large amplitude deflections (2.0 [+ or -] 1.3 mV). Two areas were identified where slow waves did not propagate, the first in the oral medial fundus and the second distal in the antrum. Finally, recordings from the entire ventral surface revealed the presence of three to five simultaneously propagating slow waves. High resolution mapping of the origin and propagation of the slow wave in the canine stomach revealed areas of high amplitude and rapid velocity, areas with fractionated low amplitude and low velocity, and areas with no propagation; all these components together constitute the elements of a gastric conduction system. slow wave; pacemaker; velocity; amplitude; gastric conduction system

In the small intestine, interstitial cells of Cajal (ICC) surrounding the myenteric plexus generate the pacemaking slow waves that are essential for an efficient intestinal transit. The underlying molecular mechanisms of the slow wave are poorly known. Our aim was to identify ICC-specific genes and their function in the mouse jejunum. Suppression subtractive hybridization using two independent ICC-deficient mouse models identified 56 genes putatively downregulated in the muscularis propria compared with wild-type littermates. Differential expression was confirmed by real-time quantitative PCR for the tyrosine kinase receptor KIT, the established marker for ICC, and for the [Na.sup.+]-[K.sup.+]-2[Cl.sup.-] cotransporter (NKCC1). Immunoreactivity for NKCC1 was detected in myenteric ICC but not in the ICC population located at the deep muscular plexus. NKCC1 was also expressed in enteric neurons and mucosal crypts. Bumetanide, an NKCC1 inhibitor, reversibly affected the shape, amplitude, and frequency of the slow waves. Similar alterations were observed in NKCC1 knockout mice. These data support the hypothesis that NKCC1 expressed in myenteric ICC is involved in the mechanism of slow waves in the murine jejunum. interstitial cells of Cajal; bumetanide; slow waves

Lammers, Wim J. E. P., Luc Ver Donck, Jan A. J. Schuurkes, and Betty Stephen. Longitudinal and circumferential spike patches in the canine small intestine in vivo. Am J Physiol Gastrointest Liver Physiol 285: G1014-G1027, 2003. First published July 3, 2003; 10.1152/ajpgi.00138. 2003.--In an open-abdominal anesthetized and fasted canine model of the intact small intestine, the presence, location, shape, and frequency of spike patches were investigated. Recordings were performed with a 240-electrode array (24 x 10, 2-mm interelectrode distance) from several sites sequentially, spanning the whole length of the small intestine. All 240 electrograms were recorded simultaneously during periods of 5 min and were analyzed to reconstruct the origin and propagation of individual spikes. At every level in the small intestine, spikes propagated in all directions before stopping abruptly, thereby activating a circumscribed area termed a 'patch.' Two types of spikes were found: longitudinal spikes, which propagated predominantly in the longitudinal direction and occurred most often in the duodenum, and a second type, circumferential spikes, which propagated predominantly in the circular direction and occurred much more frequently in the jejunum and ileum. Circumferential spikes conducted faster than longitudinal spikes (17 [+ or -] 6 and 7 [+ or -] 2 cm/s, respectively; P < 0.001). Circumferential spikes originated in >90% of all cases from the antimesenteric border, whereas longitudinal spikes were initiated all around the circumference of the intestinal tube. Finally, the spatial sequence of spike patches after the slow wave was very irregular in the upper part of the intestine but much more regular in the lower part. In conclusion, spikes and spike patches occur throughout the small intestine, whereas their type, sites of origin, extent of propagation, and frequencies of occurrence differ along the length of the small intestine, suggesting differences in local patterns of motility. slow waves; spike patches; duodenum; jejunum; ileum

Investigates whether heat shock may influence the homeostasis of intracellular calcium ions in cardiomyocytes by examining the behavior of both paced and quiescent cells isolated from nonheated and heat-shocked animals. Indication that heat stress improves relaxation after challenge with high calcium ion levels.