alpha(1)-Adrenergic receptor subtypes in rat cerebral microvessels.
To identify alpha(1)-adrenergic receptor subtypes involved in the regulation of cerebral microcirculation, we studied alpha(1)-adrenergic receptor subtypes expressed in the rat cerebral microvessels. The microvessels were prepared from rat cerebral cortex by albumin flotation and glass bead filtration techniques. [(125)I]HEAT binding to the cerebral microvessels was displaced by low concentrations of 5-methylurapidil, a selective antagonist for alpha(1A)-receptors, and modified Scatchard analysis of the data revealed that half of alpha(1)-receptors is alpha(1A)-subtype, and that alpha(1B)- and/or alpha(1D)-receptors are also present. The K(i) value of the high-affinity component for 5-methylurapidil was 3.90+/-1.08 nM, which is comparable with the value obtained in the rat cerebral cortex (2.17+/-0.88 nM). Reverse transcription and polymerase chain reaction experiments showed that mRNAs of alpha(1A)- and alpha(1B)-receptors, but not alpha(1D)-receptors, were expressed in the cerebral microvessels. These results suggest that alpha(1)-receptors involved in the regulation of cerebral microvessel function are alpha(1A)- and alpha(1B)-receptor subtypes.
Yokoo
H
H
Department of Pharmacology, Miyazaki Medical College, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan.
Kobayashi
H
H
Minami
S
S
Shiraishi
S
S
Yamamoto
R
R
Yanagita
T
T
Tsuchiya
K
K
Mohri
M
M
Wada
A
A
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D001808:Blood Vessels / Q000378:metabolism; D002560:Cerebrovascular Circulation / Q000502:physiology*; D008297:Male; D008833:Microcirculation / Q000502:physiology; D010879:Piperazines / Q000494:pharmacology; D020033:Protein Isoforms / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011942:Receptors, Adrenergic, alpha / Q000235:genetics / Q000378:metabolism*
D000317:Adrenergic alpha-Antagonists; D010879:Piperazines; D020033:Protein Isoforms; D012333:RNA, Messenger; D011942:Receptors, Adrenergic, alpha; C057446:5-methylurapidil