α-Adrenoreceptors and Muscarine Receptors in Human Pial Arteries and Micro Vessels: A Receptor Binding Study

Abstract

Summary: Human pial arteries and intraparenchymal microvessels were isolated for enzyme assays and radio ligand binding studies of receptors, Special attention was paid to contamination with brain tissue, which was as sessed by luxol staining and cerebroside assays for myelin and by scanning electron microscopy, The amount of contamination was �1% for pial vessels and 14% for microvessel preparations, Significant levels of <xj-adre noreceptors (binding sites for [3H]prazosin) and <x2-adreIn the last 20 years there has been increasing in terest in the possibility that adrenergic and cholin ergic substances play a role in the modulation of cerebral blood flow, pressure, and the permeability of the blood-brain barrier. The presence of adren ergic and cholinergic nerves in the cerebral arteries of laboratory animals has been indicated by fluo rescence microscopy (Edvinsson et a!. , 1976; Bar amidze et a!. , 1982), acetylcholinesterase staining (Borodulya and Pletchkova, 1976;Denn and Stone, 1976; Edvinsson et a!. , 1976), and electron micros copy (Iwayama et aI. , 1970; Nielsen et a!. , 197 1). In addition, responses to the application of agonists and antagonists to superficial cerebral arteries in vivo (Kuschinsky et a!. , 1974) and to isolated strips or rings of pial arteries in vitro (Duckles and Bevan, 1976; Edvinsson et aI. , 1976 Edvinsson et aI. , , 1977Lee et a!. , 1978;Duckles, 1979) have shown the presence of u-and muscarine receptors. lntraparenchymal vessels have been more difficult to study because of their location and small size. The responsiveness of these smaller vessels has been inferred from studies of Duckles, 1979;Lee et a!. , 1982). The purpose of the present study was to determine the presence of muscarine, U l -' and u2-receptors in human pial arteries and intraparenchymal micro vessels. Special emphasis was given to identifying the degree of contamination of vascular tissue with fragments of brain parenchyma. RECEPTORS IN HUMAN BLOOD VESSELS 459 METHODS Human brain tissueFrontotemporal lobes of brains from eight 20-to 50-year-old male accident victims were obtained 4-10 h postmortem. Tissue was kept at 4°C for up to I h until vessels could be isolated. Many studies attest to the sta bility of receptors and enzymes in postmortem tissue (e.g., Spokes and Koch, 1978; Puymirat et aI., 1979). Isolation of pial vesselsFrontopolar, orbital, and callosomarginal branches of the anterior cerebral artery were isolated essentially as described by Krause et al. (1980). In brief, pia-arachnoid membranes were stripped from underlying brain tissue, and pial arteries were dissected at 4°C with the help of a dissecting microscope. This procedure yields clean pial vessels, but occasional tiny pieces of brain tissue remain associated with arterioles that penetrate from pial vessels into brain parenchyma. Vessels were collected in ice-cold 0.25 M sucrose buffered with 5 mM Tr is-HCI at pH 7.4 (buffered sucrose), and homogenized in a Polytron PIO blender at top speed for 30 s. Large fragments were re moved by ...

Muscarinic Binding of Pial Vessels and Arachnoid Membrane

“…The affinity constant for pial vessels (KD = 0.097 nM) is very similar to that for arachnoid, whether it was calculated from saturation (0.039 nM) or kinetic (0.033 nM) experiments. They are in agreement with reported values for pial vessels (Ferrari-Dileo and Potter, 1985;Shimohama et al, 1985;Tsukahara et al, 1986;Vanderheyden et al, 1986), brain microvessels (Grammas et al, 1983), veins (Taniguchi et al, 1982;Brunner and Kukovetz, 1986), heart (Fields et al, 1978;Hart-zell, 1980;Hosey and Fields, 1981), and nonvascular tissues, such as brain (Yamamura and Snyder, 1974~;Hulme et al, 1978;Gilbert et al, 1979;Salvaterra et al, 1980) or gastrointestinal tract smooth muscle (Yamamura and Snyder, 19743;Nilvebrant and Sparf, 1983). The density of muscarinic receptors in pial vessels was -10-fold lower than in the arachnoid.…”

Dexmedetomidine for Neurological Surgery

“…␣ 2 -Adrenergic receptors are widely distributed within the cerebral vasculature (18,33). Much work on the adrenergic regulation of the cerebral circulation has focused on the extrinsic sympathetic innervation of arteries and pial vessels.…”

Vascular dysfunction in the pathogenesis of Alzheimer's disease — A review of endothelium-mediated mechanisms and ensuing vicious circles

“…Adrenergic receptors exist in brain microvessels, with a predominance of receptors [232][233][234][235][236][237]. Increased levels of 2 and 2 adrenoceptors have been reported in AD [237], suggesting possible alterations of the extrinsic regulation of the microvascular tone, which might contribute to impairing regional CBF distribution.…”