Unitary nature of regenerative potentials recorded from circular smooth muscle of guinea‐pig antrum

Abstract

Many gastrointestinal muscles generate rhythmic contractions that are associated with slow waves (Tomita, 1981;Sanders, 1992). Several observations suggest that activity originates in interstitial cells of Cajal (ICC), and that smooth muscle cells act as follower cells (Sanders, 1996). Thus, when regions containing ICC are cut away, slow waves are abolished (Smith et al. 1987). Similarly intestinal preparations obtained from strains of mice which lack ICC, fail to generate normal slow waves (Ward et al. 1994;Huizinga et al. 1995). In guinea-pig antrum, ICC generate large amplitude driving potentials which depolarize the circular layer. The depolarization triggers a secondary regenerative response, so giving rise to a complete slow wave (Dickens et al. 1999). Previous analyses of slow waves have suggested that they resulted from the sequential activation of voltage-dependent ion channels (Sanders, 1992). However, when single bundles of circular muscle from the antral region of guinea-pig stomach were stimulated directly, they generated regenerative potentials that did not depend upon the activation of conventional voltage-dependent ion channels. Rather they appeared to involve the voltage-activated release of internal Ca¥ following the production of a second messenger like inositol trisphosphate . Membrane depolarizations, that do not involve conventional voltage-dependent ion channels, are generated when increases in [Ca¥]é activate ion selective channels that allow an accumulation of internal positive charge (van Helden,

P2Y1 Receptors Mediate Apamin-Sensitive and -Insensitive Inhibitory Junction Potentials in Murine Colonic Circular Smooth Muscle

“…2) in the presence of atropine (3 M), guanethidine (3 M), and substance P (1 M). Unitary membrane potentials similar to those seen in other GI smooth muscle (Edwards et al, 1999;Zhang et al, 2008) were seen in all of the tissues. In some preparations spontaneous action potentials superimposed on on the IJPs induced by one and four pulses in the presence of atropine (3 M), guanethidine (3 M), substance P (1 M), and nifedipine (1 M).…”

Interstitial cells of Cajal mediate mechanosensitive responses in the stomach

“…Intramuscular ICC (ICC-IM) generate unitary potentials (20,21), and unitary potentials were enhanced during stretch (see Fig. 2).…”

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

“…The 2nd component of the slow wave may be generated by a summation of unitary potentials (Edwards et al, 1999) in response to depolarization of the membrane , and possible involvement of depolarization-activated production of IP3 has been considered Suzuki, 2000;Hirst et al, 2002a;Hirst and Ward, 2003). The generation of slow potentials is accelerated by depolarization of the membrane, and increasing the amplitude of depolarization reduces the latency to a minimum of about 1 s Hirst et al, 2002b;Kito et al, 2002b).…”