title: Substance P modulates localized calcium transients and membrane current responses in murine colonic myocytes.
abstract: 1. Neurokinins contribute to the neural regulation of gastrointestinal (GI) smooth muscles. We studied responses of murine colonic smooth muscle cells to substance P (SP) and NK(1) and NK(2) agonists using confocal microscopy and the patch clamp technique. 2. Colonic myocytes generated localized Ca(2+) transients that were coupled to spontaneous transient outward currents (STOCs). SP (10(-10) M) increased Ca(2+) transients and STOCs. Higher concentrations of SP (10(-6) M) increased basal Ca(2+) and inhibited Ca(2+) transients and STOCs. 3. Effects of SP were due to increased Ca(2+) entry via L-type Ca(2+) channels, and were mediated by protein kinase C (PKC). Nifedipine (10(-6) M) and the PKC inhibitor, GF 109203X (10(-6) M) reduced L-type Ca(2+) current and blocked the effects of SP. 4. SP responses depended upon parallel stimulation of NK(1) and NK(2) receptors. NK(1) agonist ([Sar(9),Met(O(2))(11)]-substance P; SSP) and NK(2) agonists (neurokinin A (NKA) or GR-64349) did not mimic the effects of SP alone, but NK(1) and NK(2) agonists were effective when added in combination (10(-10)-10(-6) M). Consistent with this, either an NK(1)-specific antagonist (GR-82334; 10(-7) M) or an NK(2)-specific antagonist (MEN 10,627; 10(-7) M) blocked responses to SP (10(-6) M). 5. Ryanodine (10(-5) M) blocked the increase in Ca(2+) transients and STOCs in response to SP (10(-10) M). 6. Our findings show that low concentrations of SP, via PKC-dependent enhancement of L-type Ca(2+) current and recruitment of ryanodine receptors, stimulate Ca(2+) transients. At higher concentrations of SP (10(-6) M), basal Ca(2+) increases and spontaneous Ca(2+) transients and STOCs are inhibited.
authors.affiliation: Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557-0046, U.S.A.
authors.forename: Orline
authors.initials: O
authors.lastname: Bayguinov
authors.forename: Brian
authors.initials: B
authors.lastname: Hagen
authors.forename: Kenton M
authors.initials: KM
authors.lastname: Sanders
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology; D003106:Colon / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D004553:Electric Conductivity; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D018613:Microscopy, Confocal; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D015288:Neurokinin A / Q000031:analogs & derivatives* / Q000494:pharmacology; D009529:Nicardipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010446:Peptide Fragments / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D010803:Physalaemin / Q000031:analogs & derivatives* / Q000494:pharmacology; D018039:Receptors, Tachykinin / Q000187:drug effects / Q000502:physiology; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects; D015290:Second Messenger Systems / Q000187:drug effects / Q000502:physiology; D013373:Substance P / Q000031:analogs & derivatives / Q000494:pharmacology*
chemical_list: D007093:Imidazoles; D007211:Indoles; D008301:Maleimides; D010446:Peptide Fragments; D010455:Peptides; D018039:Receptors, Tachykinin; D019837:Ryanodine Receptor Calcium Release Channel; C062618:substance P, Sar(9)-Met(O2)(11)-; C079014:GR 82334; C069192:neurokinin A(4-10), Tyr(5)-Trp(6,8,9)-Lys(10)-; C068031:neurokinin A (3-10), lysyl(3)-glycyl(8)-R-lactam-leucine(9)-; D012433:Ryanodine; D010803:Physalaemin; D013373:Substance P; C064719:iberiotoxin; D015288:Neurokinin A; D009529:Nicardipine; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; C070515:bisindolylmaleimide I