title: K(+) inward rectifier currents in reactive astrocytes from adult rat brain.
abstract: We characterized inward rectifier (K(IR)) currents in reactive astrocytes activated by CNS injury. We used primary cultures of reactive astrocytes obtained from gelatin sponge implants in adult rat brains, a system that yielded highly purified, homogeneous cultures with >95% of cells positive for GFAP, vimentin, and S-100beta. Ionic channels were studied in 1-21-day-old primary cultures using a nystatin-perforated patch clamp technique. Fast Na(+) currents were identified in <2% of cells. Most cells exhibited outward currents positive to -50 mV, with one component being sensitive to charybdotoxin, iberiotoxin, and tetraethylammonium chloride, and another component being sensitive to 4-aminopyridine. Two populations of cells were distinguished, based on presence or absence of Ba(2+)-sensitive K(IR) current negative to the K(+) reversal potential (E(k)), with >80% of cells expressing K(IR) currents. In contrast to previous reports on mammalian astrocytes, the current-voltage curve showed no appreciable current between E(k) and -50 mV, reflecting strong rectification by K(IR) channels. The magnitude of K(IR) current at -130 mV (I(-)(130)) did not change significantly during 21 days in culture (123 cells), suggesting constitutive expression of K(IR) channels. The fraction of K(IR)-negative cells was not affected by serum-starvation for 16-24 h. In cells with I(-)(130) >/= -30 pA, the membrane potential was invariably near E(k) and depolarized appreciably on addition of Ba(2+), but in cells with I(-)(130) < -30 pA, resting potentials ranged from -40 mV to -90 mV. We conclude that most adult reactive astrocytes constitutively express K(IR) channel(s) that exhibit strong rectification not previously observed in mammalian astrocytes.
authors.affiliation: Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: P R
authors.initials: PR
authors.lastname: Perillán
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.forename: J M
authors.initials: JM
authors.lastname: Simard
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000502:physiology*; D001464:Barium / Q000494:pharmacology; D001921:Brain / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000032:analysis; D018929:Cell Culture Techniques / Q000379:methods; D002478:Cells, Cultured; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D007150:Immunohistochemistry; D008564:Membrane Potentials / Q000187:drug effects; D009414:Nerve Growth Factors; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D051381:Rats; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000032:analysis; D014746:Vimentin / Q000032:analysis
chemical_list: D002135:Calcium-Binding Proteins; D005904:Glial Fibrillary Acidic Protein; D009414:Nerve Growth Factors; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; D014746:Vimentin; D001464:Barium