Involvement of stretch-activated Cl- channels in ramification of murine microglia.
A stretch-activated Cl- current (ICl) was investigated in cultured murine microglia using the whole-cell configuration of the patch-clamp technique. After application of membrane stretch, a Cl- current appeared within seconds, and its amplitude increased further within 3-8 min. ICl underwent rundown, which was prevented by addition of 4 mM ATP to the intracellular perfusing solution. The stretch-activated Cl- current exhibited outward rectification and did not show any voltage-dependent gating. Lowering the concentration of extracellular Cl- from 142 to 12 mM by equimolar substitution of Cl- with gluconate shifted the reversal potential of ICl by 41.6 +/- 1.8 mV in the depolarizing direction. 4, 4'-Diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS) blocked ICl in a voltage- and time-dependent manner. At a test potential of +40 mV, a half-maximal blockade at 16.1 microM DIDS and at 71.0 microM SITS was determined for ICl. At a concentration of 200 microM, 5-nitro-2-(3-phenylpropylamino)benzoic acid or flufenamic acid blocked ICl by 88% and 75%, respectively. Each of these four Cl- channel blockers reversibly inhibited the ramification process of microglia, whereas blockers of voltage-gated Na+ and K+ channels did not affect the transformation of microglia from their ameboid into the ramified phenotype. It is suggested that in microglia functional stretch-activated Cl- channels are required for the induction of ramification but not for maintaining the ramified shape.
Eder
C
C
Department of Neurophysiology, Institute of Physiology, Humboldt University, D 10117 Berlin, Germany.
Klee
R
R
Heinemann
U
U
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D001253:Astrocytes; D001923:Brain Chemistry / Q000502:physiology; D002478:Cells, Cultured; D018118:Chloride Channels / Q000502:physiology*; D017077:Culture Media, Conditioned / Q000494:pharmacology; D005439:Flufenamic Acid / Q000494:pharmacology; D008264:Macrophages / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008815:Mice, Inbred Strains; D017628:Microglia / Q000737:chemistry* / Q000166:cytology; D009579:Nitrobenzoates / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010812:Physical Stimulation; D013314:Stress, Mechanical; D013779:Tetrodotoxin / Q000494:pharmacology
D000894:Anti-Inflammatory Agents, Non-Steroidal; D018118:Chloride Channels; D017077:Culture Media, Conditioned; D009579:Nitrobenzoates; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D013779:Tetrodotoxin; D005439:Flufenamic Acid; D000255:Adenosine Triphosphate; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid