Vol. 278, Issue 3, H907-H912, March 2000
Serotonin 5-HT7 receptors
mediate relaxation of porcine pial veins
Takaaki
Ishine1,
Isabelle
Bouchelet2,
Edith
Hamel2, and
Tony J. F.
Lee1
1 Department of Pharmacology,
Southern Illinois University School of Medicine, Springfield,
Illinois 62794-9629; and
2 Laboratory of Cerebrovascular
Research, Montreal Neurological Institute, McGill University,
Montréal, Quebec, Canada H3A 2B4
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-HT7
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-HT7 receptors and if
5-HT7 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-HT7-receptor antagonists
(clozapine, pimozide, and LY-215840) in a concentration-dependent
manner. Furthermore, a strong PCR signal for the
5-HT7 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-HT7-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-HT7 receptors located on the
venous smooth muscle.
vasodilation; reverse transcription-polymerase chain reaction; in
vitro tissue bath; 5-HT7-messenger
ribonucleic acid; pig
