Different effect of serotonin on intracellular calcium ion dynamics in the smooth muscle cells between rat posterior ciliary artery and vorticose vein.
5-hydroxytriptamine (5-HT: serotonin) is an important transmitter that causes vessel constriction, although few studies have examined the effect of 5-HT on venous smooth muscles. The intracellular Ca(2+) concentration ([Ca(2+)]i) plays an essential role in stimulus-response coupling in numerous tissue/cells including vascular smooth muscle cells. The present study was performed to examine whether differences between arteries and veins in the response to 5-HT can be detected under confocal microscope with respect to [Ca(2+)]i dynamics. In posterior ciliary arteries of rats, 5-HT induced a [Ca(2+)]i increase. The 5-HT-induced responses were caused by both Ca(2+) influx and mobilization. Agonist and antagonist experiments revealed that arterial smooth muscles possess 5-HT1a, 1b, 2 (Gprotein-coupled type) and 5-HT3 (ion channel type) receptors, and that 5-HT2 in particular plays a major role in these responses. For vorticose veins, the 5-HT-induced responses were also caused by both Ca(2+) influx and mobilization. However, the cAMP dependent pathway (5-HT4-7) was found to be significant in vasocontraction with respect to 5-HT in these vessels. Thus, Ca(2+) mobilization was induced by 5-HT2 and 5-HT4-7 in a vessel-dependent manner, whereas Ca(2+) influx universally was induced by 5-HT3. These results indicate that the posterior ciliary arteries and vorticose veins in the same tissue might differ greatly in their responses to stimulus.
Department of Anatomy (Cell Biology), Iwate Medical University.
Masatoshi
M
Okubo
Yoh-Ichi
Y
Satoh
Masato
M
Hirakawa
Kana
K
Sasaki
Kazuki
K
Masu
Gabriel
G
J McHonde
Chika
C
Ikeda-Kurosawa
Daijiro
D
Kurosaka
Tomoyuki
T
Saino
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D019842:Ciliary Arteries / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D042541:Intracellular Space / Q000378:metabolism; D018613:Microscopy, Confocal; D057054:Molecular Imaging; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats; D012701:Serotonin / Q000494:pharmacology*; D014648:Varicose Veins / Q000188:drug therapy*
D012701:Serotonin; D002118:Calcium