title: P2Y1 receptors mediate apamin-sensitive and -insensitive inhibitory junction potentials in murine colonic circular smooth muscle.
abstract: Purinergic inhibitory neuromuscular transmission plays an important role in the control of intestinal motility. In most tissues this neurotransmission is apamin-sensitive, but recent studies in human colonic circular smooth muscle (CSM) suggest the presence of apamin-insensitive purinergic inhibitory junction potentials (IJPs). The current studies used conventional intracellular recordings on colonic CSM strips to characterize the purinergic IJPs in murine colonic CSM. P2Y1 receptor expression was examined by using reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry. The IJP induced by nerve stimulation (NS) of one and four pulses in neuronal nitric-oxide synthase knockout mice consists of an apamin-sensitive and a dominant apamin-resistant component. These are identical to the IJPs in wild-type and CD1 mice in the presence of N(omega)-nitro-l-arginine methyl ester (200 microM) and were significantly inhibited by alpha,beta-methylene ATP (50 microM), an analog of ATP. IJPs were not affected by the P2X receptor antagonist 2',3'-o-(2,4,6-trinitrophenyl)-ATP (10 microM). Furthermore, apamin-resistant IJPs induced by single-pulse NS were abolished by pyridoxal-phosphate-6-azophenyl-2',4'-disulfonate (100 microM), a P2 receptor antagonist; 2'-deoxy-N6-methyl adenosine 3,5-diphosphate (MRS-2179; 10 microM), a selective P2Y1 receptor antagonist; and tetrodotoxin (1 microM). Aboral NS induced apamin-sensitive purinergic IJPs, whereas oral and circumferential NS produced apamin-sensitive and -resistant IJPs, with the latter predominating. RT-PCR and immunohistochemistry confirmed the presence of P2Y1 receptors on smooth muscle and in the myenteric plexus. These data suggest that, depending on stimulus location, activation of P2Y1 receptors produces both apamin-sensitive and apamin-resistant IJPs in murine colonic CSM.
authors.affiliation: Gastrointestinal Diseases Research Unit, Queen's University, Kingston, Ontario, Canada.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Alan E
authors.initials: AE
authors.lastname: Lomax
authors.forename: William G
authors.initials: WG
authors.lastname: Paterson
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001030:Apamin / Q000494:pharmacology*; D003106:Colon / Q000187:drug effects / Q000502:physiology*; D054351:Electrical Synapses / Q000187:drug effects; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000502:physiology; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000502:physiology*; D058472:Receptors, Purinergic P2Y1; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: C111914:N(6)-methyl-2'-deoxyadenosine 3',5'-diphosphate; C546382:P2RY1 protein, human; C546383:P2ry1 protein, mouse; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D001030:Apamin; D013779:Tetrodotoxin; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D019001:Nitric Oxide Synthase; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D019331:NG-Nitroarginine Methyl Ester