Alpha-Adrenergic receptors in cerebral microvessels of normotensive and spontaneously hypertensive rats

Journal Article · Fri Mar 01 04:00:00 EST 1985 · Circ. Res.; (United States)

DOI:https://doi.org/10.1161/01.RES.56.3.402· OSTI ID:5549279

Kobayashi, H; Wada, A; Izumi, F; Magnoni, M S; Trabucchi, M

In rat cerebral microvessels, we characterized alpha 1- and alpha 2-adrenergic receptors, using (/sup 3/H)prazosin and (/sup 3/H)-p-amino-clonidine as radioligands. (/sup 3/H)Prazosin binding to the cerebral microvessels was saturable and of high affinity (dissociation constant of 78 pM), with a maximum binding of 48 fmol/mg protein. (/sup 3/H)Prazosin binding reached equilibrium within 15 minutes and was dissociated by the addition of 10 microM phentolamine. The inhibitory effects of isomers of norepinephrine and epinephrine on the binding showed that l-isomers were over 10 times more potent than d-isomers. (/sup 3/H)-p-Amino-clonidine binding to the cerebral microvessels was saturable and of high affinity (K/sub D/ . 0.61 nM) with a B/sub max/ of 73 fmol/mg protein. The binding reached equilibrium within 30 minutes, and was dissociated by the addition of 100 microM l-norepinephrine. l-Isomers of norepinephrine and epinephrine were over 10 times more potent than d-isomers in displacing the binding. Thus, both (/sup 3/H)prazosin and (/sup 3/H)-p-amino-clonidine bindings to the cerebral microvessels were characterized by saturability, high affinity, reversibility, and stereo-specificity. Furthermore, the specificity of both binding sites was pharmacologically evaluated by the inhibitory effects of various adrenergic agonists and antagonists on the bindings. These data indicate the existence of alpha-adrenergic receptors in the cerebral microvessels and are consistent with the hypothesis that the cerebral microcirculation is regulated by adrenergic innervation. Furthermore, the receptors were measured in cerebral microvessels of spontaneously hypertensive rats and Wistar-Kyoto controls.

• Research Organization: Univ. of Occupational and Environmental Health, Kitakyushu, Japan
• OSTI ID: 5549279
• Journal Information: Circ. Res.; (United States), Journal Name: Circ. Res.; (United States) Vol. 56:3; ISSN CIRUA
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
ADRENAL HORMONES
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BIOCHEMICAL REACTION KINETICS
BLOOD CIRCULATION
BODY
BRAIN
CARDIOTONICS
CARDIOVASCULAR AGENTS
CENTRAL NERVOUS SYSTEM
DRUGS
HORMONES
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MAMMALS
NERVOUS SYSTEM
NEUROREGULATORS
NORADRENALINE
ORGANS
RATS
REACTION KINETICS
RECEPTORS
RODENTS
STEROID HORMONES
SYMPATHOMIMETICS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES