The vasocontractive action of norepinephrine and serotonin in deep arterioles of rat cerebral gray matter.
To examine the direct effects of norepinephrine (NE) and serotonin (5-HT) on the contractility of arterioles in the gray matter of the rat cerebrum, we micro-perfused arterioles in vitro and observed the changes in luminal diameter under the stop-flow condition with constant intraluminal pressure. While the average diameter of the lumen of arterioles was 39.9 +/- 9.7 microm (n=7) in Hepes-buffered saline, the average in 10(-7) M NE in the extraluminal solution changed into smaller in saline by 21.1 +/- 5.4% (n=7). The contractile effect of NE shows a dose-dependent curve between the 10(-7) and 10(-5) M. The contractile response to 10(-6) M NE was significantly reduced by yohinbin, an alpha2 blocker. 10(-6) M NE applied to the lumen also caused contraction of arterioles by 12.4 +/- 5.3% in diameter (n=5). 5-HT at 10(-7) M in the extraluminal solution caused contraction of arterioles by 10.9 +/- 4.4% in diameter (n=7). 5-HT in the extraluminal solution caused contraction of arterioles in a dose dependent manner between 10(-10) and 10(-6) M. The contractile effect of 5-HT at 10(-6) M was strongly reduced by 10(-6) M ketanserin, a 5-HT2 receptor antagonist. 5-HT applied to the lumen had no effect at all (n=6), however NE applied to the lumen caused contraction. These results strongly suggest that 5-HT plays a significant role in arteriolar contractility only from the cerebrospinal fluid (CSF) side, while NE is an important regulator of arteriolar contractility from both the CSF and blood circulation sides.
Takahashi
R
R
Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan. ritsu@sendai.jrc.or.jp
Sakai
T
T
Furuyama
Y
Y
Kondo
Y
Y
Inoue
C N
CN
Onuma
S
S
Iinuma
K
K
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000187:drug effects; D001921:Brain / Q000098:blood supply*; D002536:Cerebral Arteries / Q000187:drug effects*; D002560:Cerebrovascular Circulation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects*
D000317:Adrenergic alpha-Antagonists; D012702:Serotonin Antagonists; D012701:Serotonin; D009638:Norepinephrine