title: Characteristics of the actions by which 5-HT affects electrical and mechanical activities in rabbit jugular vein.
abstract: OBJECTIVE
  5-HT is known to be a potent vasospasmogenic agonist in various arteries. However, in veins the vasomodulating actions of 5-HT, and the underlying mechanisms, remain to be fully clarified. Here, we characterized the actions by which 5-HT affects electrical and mechanical activities in the rabbit jugular vein.
  
  
  METHODS
  Membrane potential and isometric tension were measured in endothelium-intact and -denuded preparations. Localization of 5-HT receptor subtypes was examined immunohistochemically.
  
  
  RESULTS
  5-HT induced a transient then a small, sustained smooth muscle cell hyperpolarization in endothelium-intact strips. In endothelium-denuded strips, 5-HT induced only a sustained hyperpolarization, and this was changed to a depolarization by the selective 5-HT(7) receptor inhibitor SB269970. This depolarization was inhibited by the 5-HT(2A) receptor blocker sarpogrelate. 5-HT induced a relaxation of PGF(2α) -induced contracted strips that was similar in endothelium-intact and -denuded preparations. The latter relaxation was changed to contraction by SB269970 and this contraction was inhibited by sarpogrelate. Immunoreactive responses against endothelial and smooth muscle 5-HT(2A) receptors and smooth muscle 5-HT(7) receptors were identified in the vein. The 5-HT-induced relaxation of the PGF(2α) contraction was inhibited by the cAMP-dependent protein kinase inhibitor Rp-cAMPS and by the AC inhibitor SQ22536.
  
  
  CONCLUSIONS
  These results indicate that 5-HT activates both smooth muscle 5-HT(7) receptors (to produce relaxation) and smooth muscle 5-HT(2A) receptors (to produce contraction) in rabbit jugular vein. We suggest that in this particular vein, the 5-HT(2A) receptor-induced depolarization and contraction are masked by the 5-HT(7) receptor-induced responses, possibly via actions mediated by cAMP.
authors: Department of Pharmacology, Graduate School of Medical Sciences, Nagoya City University, Japan. titoh@med.nagoya-cu.ac.jp
authors: Takeo
authors: T
authors: Itoh
authors: Junko
authors: J
authors: Kajikuri
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015237:Dinoprost / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D005905:Glyburide / Q000494:pharmacology; D007150:Immunohistochemistry / Q000379:methods; D007537:Isometric Contraction / Q000187:drug effects; D007601:Jugular Veins / Q000187:drug effects*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism; D010636:Phenols / Q000494:pharmacology; D011817:Rabbits; D044402:Receptor, Serotonin, 5-HT2A / Q000378:metabolism; D011985:Receptors, Serotonin / Q000378:metabolism; D012701:Serotonin / Q000494:pharmacology*; D058830:Serotonin 5-HT2 Receptor Antagonists / Q000494:pharmacology; D013386:Succinates / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects
chemical_list: D010636:Phenols; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin; C404922:SB 269970; D058830:Serotonin 5-HT2 Receptor Antagonists; D013386:Succinates; D013449:Sulfonamides; C104425:serotonin 7 receptor; C017759:9-(tetrahydro-2-furyl)-adenine; C064294:sarpogrelate; D009569:Nitric Oxide; D012701:Serotonin; D015237:Dinoprost; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000225:Adenine; D005905:Glyburide