scholarly journals Properties of the inhibitory junction potential in smooth muscle of the guinea-pig gastric fundus

1996 ◽  
Vol 117 (5) ◽  
pp. 974-978 ◽  
Author(s):  
Naotomo Ohno ◽  
Lin Xue ◽  
Yoshimichi Yamamoto ◽  
Hikaru Suzuki
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Gastric Fundus ◽  
Inhibitory Junction Potential ◽  
Junction Potential

Effect of exogenous ATP on canine jejunal smooth muscle

2000 ◽  
Vol 278 (5) ◽  
pp. G725-G733 ◽  
Author(s):  
L. Xue ◽  
G. Farrugia ◽  
J. H. Szurszewski
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Pyridoxal Phosphate ◽  
Electrical Field Stimulation ◽  
Muscle Cells ◽  
Disulfonic Acid ◽  
Reactive Blue 2 ◽  
Circular Smooth Muscle ◽  
Inhibitory Junction Potential ◽  
Junction Potential

Intracellular recordings were made from the circular smooth muscle cells of the canine jejunum to study the effect of exogenous ATP and to compare the ATP response to the nonadrenergic, noncholinergic (NANC) inhibitory junction potential (IJP) evoked by electrical field stimulation (EFS). Under NANC conditions, exogenous ATP evoked a transient hyperpolarization (6.5 ± 0.6 mV) and EFS evoked a NANC IJP (17 ± 0.4 mV). ω-Conotoxin GVIA (100 nM) and a low-Ca2+, high-Mg2+ solution abolished the NANC IJP but had no effect on the ATP-evoked hyperpolarization. The ATP-evoked hyperpolarization and the NANC IJP were abolished by apamin (1 μM) and N G-nitro-l-arginine (100 μM). Oxyhemoglobin (5 μM) partially (38.8 ± 5.5%) reduced the amplitude of the NANC IJP but had no effect on the ATP-evoked hyperpolarization. Neither the NANC IJP nor the ATP-evoked hyperpolarization was affected by P2 receptor antagonists or agonists, including suramin, reactive blue 2, 1-( N, O-bis-[5-isoquinolinesulfonyl]- N-methyl-l-tyrosyl)-4-phenylpiperazine, pyridoxal phosphate-6-azophenyl-2′,4′-disulfonic acid, α,β-methylene ATP, 2-methylthioadenosine 5′-triphosphate tetrasodium salt, and adenosine 5′- O-2-thiodiphosphate. The data suggest that ATP evoked an apamin-sensitive hyperpolarization in circular smooth muscle cells of the canine jejunum via local production of NO in a postsynaptic target cell.

Functional differences of Na+/Ca2+ exchanger expression in Ca2+ transport system of smooth muscle of guinea pig stomach

2005 ◽  
Vol 83 (8-9) ◽  
pp. 791-797 ◽  
Author(s):  
Yasushi Sakai ◽  
Hiroki Kinoshita ◽  
Keiichirou Saitou ◽  
Ikuo Homma ◽  
Koji Nobe ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Guinea Pig ◽  
Gastric Fundus ◽  
Relaxation Cycle ◽  
Gastric Smooth Muscle ◽  
Guinea Pig Stomach ◽  
And Function ◽  
The Relationship ◽  
Ionophore Monensin

The plasma membrane ATP-dependent Ca2+ pump and the Na+/Ca2+ exchanger (NCX) are the major means of Ca2+ extrusion in smooth muscle. However, little is known regarding distribution and function of the NCX in guinea pig gastric smooth muscle. The expression pattern and distribution of NCX isoforms suggest a role as a regulator of Ca2+ transport in cells. Na+ pump inhibition and the consequent to removal of K+ caused gradual contraction in fundus. In contrast, the response was significantly less in antrum. Western blotting analysis revealed that NCX1 and NCX2 are the predominant NCX isoforms expressed in stomach, the former was expressed strongly in antrum, whereas the latter displayed greater expression in fundus. Isolated plasma membrane fractions derived from gastric fundus smooth muscle were also investigated to clarify the relationship between NCX protein expression and function. Na+-dependent Ca2+ uptake increased directly with Ca2+ concentration. Ca2+ uptake in Na+-loaded vesicles was markedly elevated in comparison with K+-loaded vesicles. Additionally, Ca2+ uptake by the Na+- or K+-loaded vesicles was substantially higher in the presence of A23187 than in its absence. The result can be explained based on the assumption that Na+ gradients facilitate downhill movement of Ca2+. Na+-dependent Ca2+ uptake was abolished by the monovalent cationic ionophore, monensin. NaCl enhanced Ca2+ efflux from vesicles, and this efflux was significantly inhibited by gramicidin. Results documented evidence that NCX2 isoform functionally contributes to Ca2+ extrusion and maintenance of contraction-relaxation cycle in gastric fundus smooth muscle.Key words: stomach, smooth muscle, Na+/Ca2+ exchanger (NCX), NCX2.

Suramin and the inhibitory junction potential in taenia caeci of the guinea-pig

1989 ◽  
Vol 173 (2-3) ◽  
pp. 207-209 ◽  
Author(s):  
Adriaan Den Hertog ◽  
Jan Van den Akker ◽  
Adriaan Nelemans
Keyword(s):  
Guinea Pig ◽  
Inhibitory Junction Potential ◽  
Junction Potential

ATP is a mediator of the fast inhibitory junction potential in human jejunal circular smooth muscle

1999 ◽  
Vol 276 (6) ◽  
pp. G1373-G1379 ◽  
Author(s):  
L. Xue ◽  
G. Farrugia ◽  
M. G. Sarr ◽  
J. H. Szurszewski
Keyword(s):  
Smooth Muscle ◽  
Receptor Antagonist ◽  
Receptor Agonist ◽  
Time Course ◽  
Purinergic Receptors ◽  
Fast Component ◽  
Circular Smooth Muscle ◽  
Inhibitory Junction Potential ◽  
Junction Potential

The neurotransmitter(s) that generates the fast component of the inhibitory junction potential (IJP-F) in human jejunal circular smooth muscle is not known. The aim of this study was to determine the role of ATP and purinergic receptors in the generation of the IJP-F in human jejunal circular smooth muscle strips. The P2-receptor antagonist suramin (100 μM) reduced the IJP-F by 28%. Apamin (1 μM) reduced the IJP-F by 25%. Desensitization of muscle strips with the putative P2x-receptor agonist α,β-methylene ATP (α,β-MeATP, 100 μM) decreased the IJP-F by 44%, and desensitization with the putative P2y-receptor agonist adenosine 5′- O-2-thiodiphosphate (ADPβS) completely abolished the IJP-F. Desensitization with the putative P2y-receptor agonist 2-methylthioATP had no effect on the IJP-F. Exogenous ATP evoked a hyperpolarization with a time course that matched the IJP-F. The ATP-evoked hyperpolarization was reduced by apamin and suramin, reduced by desensitization with α,β-MeATP (69% decrease), and abolished by desensitization with ADPβS. These data suggest that the IJP-F in human jejunal circular smooth muscle is mediated in part by ATP through an ADPβS-sensitive P2receptor.

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