Regional differences in 5-HT receptors in cerebral and testicular arterioles of the rat as revealed by Ca2+ imaging of real-time confocal microscopy: variances by artery size and organ specificity.
5-hydroxytriptamine (5-HT) is an important transmitter for vessel constriction. The present study was performed to clarify the effect of 5-HT on smooth muscles in large- and small-sized cerebral and testicular arterioles by confocal microscopy, with special reference to intracellular Ca2+ concentration ([Ca2+]i) dynamics. In cerebral vessels, 5-HT induced a [Ca2+]i increase and the contraction of smooth muscle cells in large- and midsized arterioles (external diameters>50 microm) but not in small-sized arterioles. Conspicuous [Ca2+]i changes by 5-HT were especially observed in the portions close to the cerebral arterial circle, and the 5-HT-induced responses were caused by both Ca2+ influx and mobilization. Experiments using agonists and antagonists also revealed that cerebral arteriole smooth muscles possess 5-HT1a, 1b, 2 (G-protein-coupled type), and 3 (ion channel type) receptors; specifically, 5-HT2 plays a major role in these responses. On the other hand, in testicular vessels, there were few regional differences among responses to 5-HT, and both large- and small-sized arterioles responded to 5-HT. The responses were caused by only Ca2+ mobilization mediated 5-HT1a and 2. These results indicate that arterioles in different tissues may respond to 5-HT in different manners. Regional differences and the size-dependent manner of responses to 5-HT in cerebral blood vessels also indicate that the regulatory mechanism of blood circulation is highly differentiated in each region of the central nervous system.
Masu
Kazuki
K
Department of Anatomy, School of Medicine, Iwate Medical University, Morioka, Japan.
Saino
Tomoyuki
T
Kuroda
Takashi
T
Matsuura
Makoto
M
Russa
Afadhali Denis
AD
Ishikita
Naoyuki
N
Satoh
Yoh-ichi
Y
D000818:Animals; D001160:Arterioles / Q000033:anatomy & histology* / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D001921:Brain / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D008297:Male; D018613:Microscopy, Confocal; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009928:Organ Specificity / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000378:metabolism*; D012701:Serotonin / Q000031:analogs & derivatives / Q000494:pharmacology; D013737:Testis / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
D011985:Receptors, Serotonin; D012701:Serotonin; D002118:Calcium