title: Are gap junctions truly involved in inhibitory neuromuscular interaction in mouse proximal colon?
abstract: 1. Gap junctions exist between circular muscle cells of the colon and between interstitial cells of Cajal (ICC) in the myenteric plexus of the gastrointestinal tract. They also probably couple intramuscular ICC with smooth muscle cells. Recent functional evidence for this was found in dye-coupling and myoelectrical experiments. 2. In the present study, we tested the hypothesis of gap junctions putatively being involved in neuromuscular interaction in mouse colon by using different classes of gap junction blockers. 3. Electrical field stimulation of the myenteric plexus elicited tetrodotoxin-sensitive and hexamethonium-independent fast and slow inhibitory junction potentials (fIJP and sIJP, respectively) in circular smooth muscle cells, as evaluated by intracellular recording techniques in impaled smooth muscle cells. Heptanol produced a time-dependent hyperpolarization of the membrane potential (MP) and abolished fIJP and sIJP. Octanol had no effect on the MP and abolished fIJP and sIJP. Carbenoxolone produced a time-dependent depolarization of the MP without any effect on fIJP or sIJP. The connexin 43 mimetic gap junction blocker GAP-27 had no effect on MP, fIJP or sIJP. 4. Based on the presently available gap junction blockers we found no evidence that gap junctions are involved in neuromuscular transmission in mouse colon, as suggested by morphological studies.
authors.affiliation: Department of Internal Medicine II, Ludwig Maximilians University Munich, Munich, Germany.
authors.forename: Andrei
authors.initials: A
authors.lastname: Sibaev
authors.forename: Birol
authors.initials: B
authors.lastname: Yüce
authors.forename: Joerg
authors.initials: J
authors.lastname: Schirra
authors.forename: Burkhard
authors.initials: B
authors.lastname: Göke
authors.forename: Hans D
authors.initials: HD
authors.lastname: Allescher
authors.forename: Martin
authors.initials: M
authors.lastname: Storr
mesh_terms: D000818:Animals; D002229:Carbenoxolone / Q000494:pharmacology; D002450:Cell Communication; D003106:Colon / Q000294:innervation* / Q000502:physiology; D017630:Connexins / Q000494:pharmacology; D004558:Electric Stimulation; D017629:Gap Junctions / Q000187:drug effects / Q000502:physiology*; D019850:Heptanol / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials; D051379:Mice; D008807:Mice, Inbred BALB C; D009130:Muscle, Smooth / Q000294:innervation / Q000502:physiology; D009197:Myenteric Plexus / Q000502:physiology; D009469:Neuromuscular Junction / Q000187:drug effects / Q000502:physiology*; D009842:Oligopeptides; D009435:Synaptic Transmission; D013997:Time Factors
chemical_list: D017630:Connexins; D009842:Oligopeptides; C455880:gap 27 peptide; D019850:Heptanol; D002229:Carbenoxolone