title: Heterogeneity of muscarinic receptor subtypes in cerebral blood vessels.
abstract: The identity and distribution of muscarinic cholinergic receptor subtypes and associated signal transduction mechanisms was characterized for the cerebral circulation using correlated functional and biochemical investigations. Subtypes were distinguished by the relative affinities of a panel of muscarinic antagonists, pirenzepine, AF-DX 116 [11-2-[[2-[diethylaminomethyl]- 1-piperidinyl]acetyl]-5,11-dihydro-6H- pyrido[2,3-b][1,4]benzodiazepine-6-one], hexahydrosiladifenidol, methoctramine, 4-diphenylacetoxy-N-methylpiperidine methobromide, dicyclomine, para-fluoro-hexahydrosiladifenidol and atropine. Muscarinic receptors characterized by inhibition of [3H]quinuclidinylbenzilate binding in membranes of bovine pial arteries were of the M2 subtype. In contrast pharmacological analysis of [3H]-quinuclidinylbenzilate binding in bovine intracerebral microvessels suggests the presence of an M4 subtype. Receptors mediating endothelium-dependent vasodilation in rabbit pial arteries were of the M3 subtype, whereas muscarinic receptors stimulating endothelium-independent phosphoinositide hydrolysis in bovine pial arteries were of the M1 subtype. These findings suggest that characteristics of muscarinic receptors in cerebral blood vessels vary depending on the type of vessel, cellular location and function mediated.
authors.affiliation: Department of Pharmacology, College of Medicine, University of California, Irvine.
authors.forename: A L
authors.initials: AL
authors.lastname: Garcia-Villalon
authors.forename: D N
authors.initials: DN
authors.lastname: Krause
authors.forename: F J
authors.initials: FJ
authors.lastname: Ehlert
authors.forename: S P
authors.initials: SP
authors.lastname: Duckles
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002536:Cerebral Arteries / Q000378:metabolism*; D002560:Cerebrovascular Circulation; D005260:Female; D008297:Male; D010277:Parasympathomimetics / Q000037:antagonists & inhibitors*; D010716:Phosphatidylinositols / Q000378:metabolism; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D011817:Rabbits; D011869:Radioligand Assay; D011976:Receptors, Muscarinic / Q000378:metabolism*; D014316:Tritium
chemical_list: D010277:Parasympathomimetics; D010716:Phosphatidylinositols; D011976:Receptors, Muscarinic; D014316:Tritium; D011813:Quinuclidinyl Benzilate