title: Participation of ATP in nonadrenergic, noncholinergic relaxation of longitudinal muscle of wistar rat jejunum.
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 muM) 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 muM), significantly inhibited the relaxations. The exogenous ATP-induced 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.
authors.affiliation: Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, Osaka Prefecture University, Sakai, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Waseda
authors.forename: Tadayoshi
authors.initials: T
authors.lastname: Takeuchi
authors.forename: Mayuko
authors.initials: M
authors.lastname: Ohta
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Okishio
authors.forename: Akikazu
authors.initials: A
authors.lastname: Fujita
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Hata
authors.forename: Tadashi
authors.initials: T
authors.lastname: Takewaki
mesh_terms: D000250:Adenosine Phosphosulfate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D004334:Drug Administration Schedule; D004558:Electric Stimulation / Q000379:methods; D006145:Guanethidine / Q000494:pharmacology; D007082:Ileum / Q000187:drug effects; D007583:Jejunum / Q000187:drug effects / Q000473:pathology* / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009126:Muscle Relaxation / Q000187:drug effects* / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000473:pathology / Q000502:physiology; D009496:Neurotensin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D010208:Papaverine / Q000494:pharmacology; D058914:Purinergic Antagonists; D058919:Purinergic P2 Receptor Antagonists; D011720:Pyrazoles / Q000037:antagonists & inhibitors / Q000494:pharmacology; D011804:Quinolines / Q000037:antagonists & inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011983:Receptors, Purinergic / Q000008:administration & dosage; D018048:Receptors, Purinergic P2 / Q000502:physiology; D019284:Thapsigargin / Q000378:metabolism / Q000494:pharmacology
chemical_list: D058914:Purinergic Antagonists; D058919:Purinergic P2 Receptor Antagonists; D011720:Pyrazoles; D011804:Quinolines; D011983:Receptors, Purinergic; D018048:Receptors, Purinergic P2; C079087:SR 48692; D001030:Apamin; D009496:Neurotensin; D000250:Adenosine Phosphosulfate; D019284:Thapsigargin; D001285:Atropine; D000255:Adenosine Triphosphate; D010208:Papaverine; D006145:Guanethidine