title: Serotonin 5-HT(7) receptors mediate relaxation of porcine pial veins.
abstract: Isolated porcine pial veins in the presence of active muscle tone have been shown to exhibit rhythmic contractions (RC) that are inhibited by serotonin (5-HT) in a concentration-dependent manner. The 5-HT inhibition of RC is mediated by an as yet unidentified 5-HT receptor subtype located on the vascular smooth muscle. 5-carboxamidotryptamine, which is a potent but nonselective agonist at 5-HT(7) receptors, has been shown to be the most potent inhibitor of RC in porcine pial veins. Therefore, the present study was designed to determine if the 5-HT-mediated inhibition of RC in pial veins is mediated by 5-HT(7) receptors and if 5-HT(7) receptor mRNA is expressed in endothelium-denuded pial veins; the study was done with the use of an in vitro tissue bath and RT-PCR techniques. Our findings indicated that 5-HT inhibition of RC in porcine pial veins was prevented by 5-HT(7)-receptor antagonists (clozapine, pimozide, and LY-215840) in a concentration-dependent manner. Furthermore, a strong PCR signal for the 5-HT(7) receptor was consistently detected in endothelium-denuded pial veins. Sequence analysis of the amplified products confirmed their high degree of homology with the porcine and/or human 5-HT(7)-receptor gene. Taken together, these data suggest that the 5-HT-induced inhibition of RC in porcine pial veins is at least in part mediated by 5-HT(7) receptors located on the venous smooth muscle.
authors.affiliation: Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois 62794-9629, USA.
authors.forename: T
authors.initials: T
authors.lastname: Ishine
authors.forename: I
authors.initials: I
authors.lastname: Bouchelet
authors.forename: E
authors.initials: E
authors.lastname: Hamel
authors.forename: T J
authors.initials: TJ
authors.lastname: Lee
mesh_terms: D000818:Animals; D005260:Female; D015870:Gene Expression; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D010841:Pia Mater / Q000098:blood supply*; D012333:RNA, Messenger / Q000032:analysis; D011985:Receptors, Serotonin / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D013552:Swine; D014680:Veins / Q000502:physiology
chemical_list: D012333:RNA, Messenger; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; C104425:serotonin 7 receptor; D012701:Serotonin