title: Properties of submucosal venules in the rat distal colon.
abstract: OBJECTIVE
  Venules within the gut wall may have intrinsic mechanisms for maintaining the circulation even upon the intestinal wall distension. We aimed to explore spontaneous and nerve-mediated contractile activity of colonic venules.
  
  
  METHODS
  Changes in the diameter of submucosal venules of the rat distal colon were measured using video microscopy. The innervation of the microvasculature was investigated using fluorescence immunohistochemistry.
  
  
  RESULTS
  Submucosal venules exhibited spontaneous constrictions that were abolished by blockers of L-type Ca(2+) channels (1 μM nicardipine), Ca(2+)-ATPase (10 μM cyclopiazonic acid), IP3 receptor (100 μM 2-APB), Ca(2+)-activated Cl(-) channels (100 μM DIDS) or store-operated Ca(2+) entry channels (10 μM SKF96365). Transmural nerve stimulation (TNS at 10 Hz) induced a phasic venular constriction that was blocked by phentolamine (1 μM, α-adrenoceptor antagonist) or sympathetic nerve depletion using guanethidine (10 μM). Stimulation of primary afferent nerves with TNS (at 20 Hz) or capsaicin (100 nM) evoked a sustained venular dilatation that was attenuated by calcitonin gene-related peptide (CGRP) 8-37 (2 μM), a CGRP receptor antagonist. Immunohistochemistry revealed sympathetic and primary afferent nerves running along submucosal venules.
  
  
  CONCLUSIONS
  Submucosal venules of the rat distal colon exhibit spontaneous constrictions that appear to primarily rely on Ca(2+) release from sarcoplasmic reticulum and subsequent opening of Ca(2+)-activated Cl(-) channels that trigger Ca(2+) influx through L-type Ca(2+) channels. Venular contractility is modulated by sympathetic as well as CGRP-containing primary afferent nerves, suggesting that submucosal venules may play an active role in regulating the microcirculation of the digestive tract.
authors.affiliation: Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Retsu
authors.initials: R
authors.lastname: Mitsui
authors.forename: Shun
authors.initials: S
authors.lastname: Miyamoto
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Takano
authors.forename: Hikaru
authors.initials: H
authors.lastname: Hashitani
mesh_terms: D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D020013:Calcium Signaling; D003106:Colon / Q000098:blood supply*; D004558:Electric Stimulation; D017615:Enteric Nervous System / Q000187:drug effects / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D008297:Male; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D051381:Rats; D017208:Rats, Wistar; D013373:Substance P / Q000378:metabolism; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology; D014699:Venules / Q000187:drug effects / Q000294:innervation / Q000378:metabolism
chemical_list: D014665:Vasodilator Agents; D013373:Substance P; D015740:Calcitonin Gene-Related Peptide
keywords: afferent nerve; autonomic nerve; intestine; microvasculature; neuropeptide