title: Distinct roles of nitric oxide synthases and interstitial cells of Cajal in rectoanal relaxation.
abstract: Nitric oxide (NO) relaxes the internal anal sphincter (IAS), but its enzymatic source(s) remains unknown; neuronal (nNOS) and endothelial (eNOS) NO synthase (NOS) isoforms could be involved. Also, interstitial cells of Cajal (ICC) may be involved in IAS relaxation. We studied the relative roles of nNOS, eNOS, and c-Kit-expressing ICC for IAS relaxation using genetic murine models. The basal IAS tone and the rectoanal inhibitory reflex (RAIR) were assessed in vivo by a purpose-built solid-state manometric probe and by using wild-type, nNOS-deficient (nNOS-/-), eNOS-deficient (eNOS-/-), and W/W(v) mice (lacking certain c-Kit-expressing ICC) with or without L-arginine or N(omega)-nitro-L-arginine methyl ester (L-NAME) treatment. Moreover, the basal tone and response to electrical field stimulation (EFS) were studied in organ bath using wild-type and mutant IAS. In vivo, the basal tone of eNOS-/- was higher and W/W(v) was lower than wild-type and nNOS-/- mice. L-arginine administered rectally, but not intravenously, decreased the basal tone in wild-type, nNOS-/-, and W/W(v) mice. However, neither L-arginine nor L-NAME affected basal tone in eNOS-/- mice. In vitro, L-arginine decreased basal tone in wild-type and nNOS-/- IAS but not in eNOS-/- or wild-type IAS without mucosa. The in vivo RAIR was intact in wild-type, eNOS-/-, and W/W(v) mice but absent in all nNOS-/- mice. EFS-induced IAS relaxation was also reduced in nNOS-/- IAS. Thus the basal IAS tone is largely controlled by eNOS in the mucosa, whereas the RAIR is controlled by nNOS. c-Kit-expressing ICC may not be essential for the RAIR.
authors.affiliation: Center of Swallowing and Motility Disorders, Department of Veterans Affairs Medical Center, 1400 VFW Parkway, West Roxbury, MA 02132, USA.
authors.forename: Akiko
authors.initials: A
authors.lastname: Terauchi
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kobayashi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Mashimo
mesh_terms: D001003:Anal Canal / Q000294:innervation / Q000502:physiology; D000818:Animals; D001120:Arginine / Q000494:pharmacology; D004558:Electric Stimulation; D017615:Enteric Nervous System / Q000166:cytology / Q000201:enzymology*; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009433:Neural Inhibition / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D011312:Pressure; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D012007:Rectum / Q000294:innervation* / Q000502:physiology*; D012018:Reflex / Q000502:physiology
chemical_list: D009419:Nerve Tissue Proteins; D001120:Arginine; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496321:Nos1 protein, mouse; C496315:Nos3 protein, mouse; D019009:Proto-Oncogene Proteins c-kit; D019331:NG-Nitroarginine Methyl Ester