title: Astrocytes cultured from specific brain regions differ in their expression of adrenergic binding sites.
abstract: We sought to characterize regional heterogeneity of astrocytes using adrenergic receptor sites as cellular markers. Primary cultures made from 6 regions of neonatal rat brain consisted almost exclusively of astrocytes. Membranes from astrocytes cultured 1-3 weeks were prepared for radioligand binding assays of beta- and alpha 2-adrenergic sites using the ligands [3H]dihydroalprenolol and [3H]p-aminoclonidine, respectively. Receptor expression was not affected by time in culture. Astrocytes from different brain regions varied up to 3-fold with respect to number but not affinity for both classes of adrenergic binding site with a rank order of cerebral cortex = superior colliculus greater than hippocampus = ventral midbrain greater than or equal to caudate nucleus greater than or equal to hypothalamus. Binding to beta- and alpha 2-adrenergic receptors was positively correlated across brain regions. Astrocytic receptor binding in each region did not correspond to total receptor levels assessed by quantitative autoradiography. We conclude that: (a) astrocytes are markedly heterogeneous between major brain regions with respect to expression of adrenergic binding sites; (b) regional variations in the density of adrenergic binding sites in brain reflect, in part, local specialization of astrocytes; and (c) a substantial proportion of the adrenergic binding sites in some brain regions may be on astrocytes.
authors.affiliation: Division of Neurobiology, Cornell University Medical College, New York, NY 10021.
authors.forename: P
authors.initials: P
authors.lastname: Ernsberger
authors.forename: L
authors.initials: L
authors.lastname: Iacovitti
authors.forename: D J
authors.initials: DJ
authors.lastname: Reis
mesh_terms: D000526:Alprenolol / Q000031:analogs & derivatives*; D000818:Animals; D001253:Astrocytes / Q000166:cytology* / Q000378:metabolism; D001921:Brain / Q000166:cytology* / Q000378:metabolism; D002478:Cells, Cultured; D003000:Clonidine / Q000031:analogs & derivatives* / Q000378:metabolism; D004082:Dihydroalprenolol / Q000378:metabolism*; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D051381:Rats; D011941:Receptors, Adrenergic / Q000378:metabolism*
chemical_list: D005904:Glial Fibrillary Acidic Protein; D011941:Receptors, Adrenergic; D004082:Dihydroalprenolol; C016986:apraclonidine; D000526:Alprenolol; D003000:Clonidine