Electrical Coupling between the Myenteric Interstitial Cells of Cajal and Adjacent Muscle Layers in the Guinea‐Pig Gastric Antrum

Abstract

Intracellular recordings were made from short segments of the muscular wall of the guinea-pig gastric antrum. Preparations were impaled using two independent microelectrodes, one positioned in the circular layer and the other either in the longitudinal layer, in the network of myenteric interstitial cells of Cajal (ICC MY ) or in the circular layer. Cells in each layer displayed characteristic patterns of rhythmical activity, with the largest signals being generated by ICC MY . Current pulses injected into the circular muscle layer produced electrotonic potentials in each cell layer, indicating that the layers are electrically interconnected. The amplitudes of these electrotonic potentials were largest in the circular layer and smallest in the longitudinal layer. An analysis of electrical coupling between the three layers suggests that although the cells in each layer are well coupled to neighbouring cells, the coupling between either muscle layer and the network of ICC MY is relatively poor. The electrical connections between ICC MY and the circular layer did not rectify. In parallel immunohistochemical studies, the distribution of the connexins Cx40, Cx43 and Cx45 within the antral wall was determined. Only Cx43 was detected; it was widely distributed on ICC MY and throughout the circular smooth muscle layer, being concentrated around ICC IM , but was less abundant in the circular muscle layer immediately adjacent to ICC MY . Although the electrophysiological studies indicate that smooth muscle cells in the longitudinal muscle layer are electrically coupled to each other, none of the connexins examined were detected in this layer.

Metabolic component of the temperature-sensitivity of slow waves recorded from gastric muscle of the guinea-pig

“…For pacemaker and follower potentials, the first three parameters showed similar temperature sensitivity. Follower potentials and the 1st component of slow waves are formed by an electrotonic spread of pacemaker potentials to longitudinal and circular smooth muscles, respectively (Dickens et al, 1999;Cousins et al, 2003). The 2nd component of slow waves is formed by slow potentials generated in circular muscles (Dickens et al, 1999;Cousins et al, 2003), and the results indicate that the temperature sensitivities of parameters for slow waves are similar to those for pacemaker potentials.…”

“…Follower potentials and the 1st component of slow waves are formed by an electrotonic spread of pacemaker potentials to longitudinal and circular smooth muscles, respectively (Dickens et al, 1999;Cousins et al, 2003). The 2nd component of slow waves is formed by slow potentials generated in circular muscles (Dickens et al, 1999;Cousins et al, 2003), and the results indicate that the temperature sensitivities of parameters for slow waves are similar to those for pacemaker potentials. These results indicate that, although the conduction of electrical signals from ICC-MY to smooth muscle cells is a decremental phenomenon (Edwards and Hirst, 2005), temperature-induced changes in pacemaker potentials are conducted to smooth muscles, possibly through gap junctions, at all temperatures examined.…”

“…Pacemaker potentials generated in ICC-MY propagate to both circular and longitudinal smooth muscle cells in an electrotonic manner (Dickens et al, 1999;Cousins et al, 2003). However, the shapes of slow waves differ from follower potentials, despite both potentials being produced by electrotonic spread of pacemaker potentials.…”

Effects of Dai-kenchu-to on spontaneous activity in the mouse small intestine

“…ICC-MY generate pacemaker potentials periodically (Kito and Suzuki, 2003;Kito et al, 2005). Pacemaker potentials are conducted in an electrotonic way to smooth muscle layers (circular and longitudinal layers) to generate slow waves (Cousins et al, 2003;Hirst and Ward, 2003).…”

Interstitial cells of Cajal mediate mechanosensitive responses in the stomach

“…Slow waves, initiated in the corpus, actively propagate around and along the length of the stomach and entrain the activity of distal pacemakers. ICC-MY are electrically coupled to smooth muscle cells of the gastric wall (6), and slow waves conduct into the musculature, causing depolarization of smooth muscle cells, an increase in the open probability of voltage-dependent Ca 2ϩ channels, Ca 2ϩ entry, and phasic contractions (7). Contractions initiated by slow waves are the basis for the gastric peristalsis that is essential for proper processing of solid foods and gastric emptying.…”