title: Microglial K(+) channel expression in young adult and aged mice.
abstract: The K(+) channel expression pattern of microglia strongly depends on the cells' microenvironment and has been recognized as a sensitive marker of the cells' functional state. While numerous studies have been performed on microglia in vitro, our knowledge about microglial K(+) channels and their regulation in vivo is limited. Here, we have investigated K(+) currents of microglia in striatum, neocortex and entorhinal cortex of young adult and aged mice. Although almost all microglial cells exhibited inward rectifier K(+) currents upon membrane hyperpolarization, their mean current density was significantly enhanced in aged mice compared with that determined in young adult mice. Some microglial cells additionally exhibited outward rectifier K(+) currents in response to depolarizing voltage pulses. In aged mice, microglial outward rectifier K(+) current density was significantly larger than in young adult mice due to the increased number of aged microglial cells expressing these channels. Aged dystrophic microglia exhibited outward rectifier K(+) currents more frequently than aged ramified microglia. The majority of microglial cells expressed functional BK-type, but not IK- or SK-type, Ca(2+) -activated K(+) channels, while no differences were found in their expression levels between microglia of young adult and aged mice. Neither microglial K(+) channel pattern nor K(+) channel expression levels differed markedly between the three brain regions investigated. It is concluded that age-related changes in microglial phenotype are accompanied by changes in the expression of microglial voltage-activated, but not Ca(2+) -activated, K(+) channels.
authors.affiliation: Institute for Infection and Immunity, St. George's, University of London; Cranmer Terrace, London, SW17 0RE, United Kingdom.
authors.forename: Tom
authors.initials: T
authors.lastname: Schilling
authors.forename: Claudia
authors.initials: C
authors.lastname: Eder
mesh_terms: D000375:Aging; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003342:Corpus Striatum / Q000166:cytology*; D004594:Electrophysiology / Q000379:methods; D018728:Entorhinal Cortex / Q000166:cytology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000378:metabolism / Q000502:physiology*; D015221:Potassium Channels / Q000378:metabolism* / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology
chemical_list: D015221:Potassium Channels; D002118:Calcium
keywords: aging; brain macrophages; development; ion channels; potassium channels