ATP is a mediator of the fast inhibitory junction potential in human jejunal circular smooth muscle.
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 microM) reduced the IJP-F by 28%. Apamin (1 microM) reduced the IJP-F by 25%. Desensitization of muscle strips with the putative P2x-receptor agonist alpha, beta-methylene ATP (alpha,beta-MeATP, 100 microM) decreased the IJP-F by 44%, and desensitization with the putative P2y-receptor agonist adenosine 5'-O-2-thiodiphosphate (ADPbetaS) 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 alpha,beta-MeATP (69% decrease), and abolished by desensitization with ADPbetaS. These data suggest that the IJP-F in human jejunal circular smooth muscle is mediated in part by ATP through an ADPbetaS-sensitive P2 receptor.
Xue
L
L
Department of Physiology and Biophysics, Mayo Clinic, Rochester, Minnesota 55905, USA.
Farrugia
G
G
Sarr
M G
MG
Szurszewski
J H
JH
D000255:Adenosine Triphosphate / Q000494:pharmacology / Q000502:physiology*; D004558:Electric Stimulation; D004594:Electrophysiology; D017629:Gap Junctions / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D007583:Jejunum / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D011930:Reaction Time / Q000502:physiology
D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D000255:Adenosine Triphosphate; D019001:Nitric Oxide Synthase