title: Role of voltage-gated K(+) channels in regulating Ca(2+) entry in rat cortical astrocytes.
abstract: Astrocytes have multiple functions such as provision of nourishment and mechanical support to the nervous system, helping to clear extracellular metabolites of neurons and modulating synaptic transmission by releasing gliotransmitters. In excitable cells, voltage-gated K(+) (Kv) channels serve to repolarize during action potentials. Astrocytes are considered non-excitable cells since they are not able to generate action potentials. There is an abundant expression of various Kv channels in astrocytes but the functions of these Kv channels remain unclear. We examined whether these astrocyte Kv channels regulate astrocyte "excitability" in the form of cytosolic Ca(2+) signaling. Electrophysiological examination revealed that neonatal rat cortical astrocytes possessed both delayed rectifier type and A-type Kv channels. Pharmacological blockade of both delayed rectifier Kv channels by TEA and A-type Kv channels by quinidine significantly suppressed store-operated Ca(2+) influx; however, TEA alone or quinidine alone did not suffice to cause such suppression. TEA and quinidine together dramatically enhanced current injection-triggered membrane potential overshoot (depolarization); either drug alone caused much smaller enhancements. Taken together, the results suggest both delayed rectifier and A-type Kv channels regulate astrocyte Ca(2+) signaling via controlling membrane potential.
authors.affiliation: Department of Anesthesiology, E-Da Hospital, I-Shou University, Kaohsiung, Taiwan.
authors.forename: King-Chuen
authors.initials: KC
authors.lastname: Wu
authors.forename: Chang-Shin
authors.initials: CS
authors.lastname: Kuo
authors.forename: Chia-Chia
authors.initials: CC
authors.lastname: Chao
authors.forename: Chieh-Chen
authors.initials: CC
authors.lastname: Huang
authors.forename: Yuan-Kun
authors.initials: YK
authors.lastname: Tu
authors.forename: Paul
authors.initials: P
authors.lastname: Chan
authors.forename: Yuk-Man
authors.initials: YM
authors.lastname: Leung
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004594:Electrophysiology / Q000379:methods; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024642:Potassium Channels, Voltage-Gated / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
chemical_list: D026902:Potassium Channel Blockers; D024642:Potassium Channels, Voltage-Gated; D002118:Calcium