Properties of the inhibitory junction potential in smooth muscle of the guinea‐pig gastric fundus

Ohno, Naotomo; Lü, Xue; Yamamoto, Yasutake; Suzuki, Hiroyoshi

doi:10.1111/j.1476-5381.1996.tb15290.x

Cited by 35 publications

(33 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…EFS-induced fast inhibitory junction potentials (i.j.ps) were suggested to be mediated by ATP and to be apamin-sensitive in the circular muscle of the human jejunum (11), the guinea pig ileum (12), the rat colon (13), the guinea pig colon (14), and the mouse distal colon (15). Although these results suggest a role of ATP in NANC relaxation, several reports present contradictory results: no role for ATP was suggested in the rat ileum (16), proximal colon (17), and caecum (18) and the guinea pig gastric fundus (19). This discrepancy may be due to the regional, species, and strain differences in the mediator of NANC relaxation (20,21).…”

Section: Introductionmentioning

confidence: 59%

Participation of ATP in Nonadrenergic, Noncholinergic Relaxation of Longitudinal Muscle of Wistar Rat Jejunum

et al. 2005

View full text Add to dashboard Cite

Abstract. A role of ATP in nonadrenergic, noncholinergic (NANC) relaxations was examined in the Wistar rat jejunum. Electrical field stimulation (EFS) induced NANC relaxation of longitudinal muscle of the jejunal segments in a frequency-dependent manner. A purinoceptor antagonist, adenosine 3'-phosphate 5'-phosphosulfate (A3P5PS, 100 mM) inhibited the relaxation: relaxations induced by EFS at lower or higher frequencies were either completely or partially inhibited, respectively. After the jejunal segments had been desensitized to ATP, the relaxations were decreased to the same extent as those inhibited by A3P5PS. An inhibitor of small conductance Ca 2+-activated K + channels (SK channels), apamin (100 nM), completely inhibited EFS-induced relaxations. Treatment of the segments with an inhibitor of sarcoplasmic reticulum Ca 2+ -ATPase, thapsigargin (1 mM), significantly inhibited the relaxations. The exogenous ATPinduced relaxation of longitudinal muscle occurred with a concomitant decrease in intracellular Ca 2+ levels. Apamin and thapsigargin abolished these ATP-induced responses. A3P5PS significantly inhibited the inhibitory junction potentials which were induced in the longitudinal muscle cells. In addition, apamin significantly inhibited the hyperpolarization that was induced by exogenous ATP in the cells. These findings in the Wistar rat jejunum suggest that ATP participates in the NANC relaxation via activation of SK channels induced by Ca 2+ ions that are released from the thapsigargin-sensitive store site.

show abstract

Section: Introductionmentioning

confidence: 59%

Participation of ATP in Nonadrenergic, Noncholinergic Relaxation of Longitudinal Muscle of Wistar Rat Jejunum

et al. 2005

View full text Add to dashboard Cite

show abstract

“…ATP and intrinsic inhibitory nerve stimulation elicit responses that are reduced or blocked by apamin and thus are considered to be due to activation of SK channels (19,32). The inhibitory actions of ATP are thought to be mediated by P2Y receptors (10,19), and we have recently described a mechanism of how activation of P2Y receptors can couple to activation of apamin-sensitive SK channels in the murine colonic smooth muscle cells (14). In the present study, we have investigated a mechanism of active repolarization that appears to participate in the restoration of resting membrane potentials after apamin-sensitive (fast) IJPs and responses to localized application of ATP.…”

Section: Discussionmentioning

confidence: 99%

Mechanism of active repolarization of inhibitory junction potential in murine colon

Baker

Mutafova‐Yambolieva

Monaghan

et al. 2003

American Journal of Physiology-Gastrointestinal and Liver Physi

View full text Add to dashboard Cite

. Mechanism of active repolarization of inhibitory junction potential in murine colon. Am J Physiol Gastrointest Liver Physiol 285: G813-G821, 2003; 10.1152/ajpgi. 00115.2003.-Enteric inhibitory responses in gastrointestinal (GI) smooth muscles involve membrane hyperpolarization that transiently reduce the excitability of GI muscles. We examined the possibility that an active repolarization mechanism participates in the restoration of resting membrane potential after fast inhibitory junction potentials (IJPs) in the murine colon. Previously, we showed these cells express a voltage-dependent nonselective cation conductance (NSCC) that might participate in active repolarization of IJPs. Colonic smooth muscle cells were impaled with microelectrodes and voltage responses to nerve-evoked IJPs, and locally applied ATP were recorded. Ba 2ϩ (500 M), a blocker of the NSCC, slowed the rate of repolarization of IJPs. We also tested the effects of Ba 2ϩ , Ni 2ϩ , and mibefradil, all blockers of the NSCC, on responses to locally applied ATP. Spritzes of ATP caused transient hyperpolarization, and the durations of these responses were significantly increased by the blockers of the NSCC. We considered whether NSCC blockers might affect ATP metabolism and found that Ni 2ϩ decreased ATP breakdown in colonic muscles. Mibefradil had no effect on ATP metabolism. Because both Ni 2ϩ and mibefradil had similar effects on prolonging responses to ATP, it appears that restoration of resting membrane potential after ATP spritzes is not primarily due to ATP metabolism. Neurally released enteric inhibitory transmitter and locally applied ATP resulted in transient hyperpolarizations of murine colonic muscles. Recovery of membrane potential after these responses appears to involve an active repolarization mechanism due to activation of the voltage-dependent NSCC expressed by these cells. gastrointestinal motility; adenosine 5Ј-triphosphate; voltagedependent nonselective cation current GASTROINTESTINAL (GI) motility is orchestrated by the enteric nervous system activating and inhibiting GI muscles in orderly patterns. The inhibitory component of neuromuscular regulation comes from release of several neurotransmitter substances, including ATP, NO, and peptides (4, 10, 21). In GI muscles such as human, murine, and guinea pig colon, release of ATP during nerve stimulation evokes a fast inhibitory junction potential (IJP), which transiently takes the membrane potentials of smooth muscle cells toward the equilibrium potential for the K ϩ ionic gradient (hyperpolarization) (8,22). Release of NO during the same period results in a smaller amplitude and longer-duration hyperpolarization phase that can outlast the fast phase of the IJP by several times. The fast hyperpolarization arises from activation of apamin-sensitive, small-conductance Ca 2ϩ -activated K ϩ channels (SK) (14), and the slow phase of the IJP is due to NOdependent stimulation of cyclic GMP production, activation of protein kinase G, and activation of NO-dependent K conductance(s) (5,...

show abstract

“…Inhibition by neurogenic NO of the release of acetylcholine from stimulated neurons was also determined in the canine ileum previously incubated with 3 H-choline (Hryhorenko et al, 1994). In the guinea pig gastric fundus, NO released from inhibitory nerves reduced the cholinergic neurotransmission (Ohno et al, 1996). According to Yoneda and Suzuki (2001), it appears that the suppression of excitatory junctional po-328 TODA AND HERMAN tentials is mainly a prejunctional event and that the depression of mechanical responses is mainly induced postjunctionally.…”

Section: Prejunctional Regulationmentioning

confidence: 99%

Gastrointestinal Function Regulation by Nitrergic Efferent Nerves

Toda

Herman

2005

Pharmacol Rev

View full text Add to dashboard Cite

Properties of the inhibitory junction potential in smooth muscle of the guinea‐pig gastric fundus

Cited by 35 publications

References 26 publications

Participation of ATP in Nonadrenergic, Noncholinergic Relaxation of Longitudinal Muscle of Wistar Rat Jejunum

Participation of ATP in Nonadrenergic, Noncholinergic Relaxation of Longitudinal Muscle of Wistar Rat Jejunum

Mechanism of active repolarization of inhibitory junction potential in murine colon

Gastrointestinal Function Regulation by Nitrergic Efferent Nerves

Contact Info

Product

Resources

About