Inward and outward rectifying potassium currents set membrane potentials in activated rat microglia

Area of Science:

• Neuroscience
• Cell Biology
• Electrophysiology

Background:

• Microglia are key immune cells in the central nervous system.
• Microglial activation by lipopolysaccharide (LPS) is a critical process in neuroinflammation.
• Ion channel activity significantly influences cell membrane potential and function.

Purpose of the Study:

• To investigate the role of potassium currents in setting the membrane potential of LPS-activated rat microglia.
• To differentiate the contributions of inward rectifying K+ (K(IR)) and outward rectifying K+ (K(V)) currents.

Main Methods:

• Utilized whole-cell patch-clamp techniques to measure ion currents and membrane potentials.
• Applied lipopolysaccharide (LPS) to activate cultured rat microglial cells.
• Used barium ions (Ba2+) to selectively block K(IR) currents.

Main Results:

• LPS activation induced outward rectifying K+ (K(V)) currents in addition to existing inward rectifying K+ (K(IR)) currents.
• K(V) current was found to directly set the membrane potential to approximately -45 mV.
• Microglial membrane potentials exhibited two peaks, around -45 mV and -70 mV, corresponding to K(V) and K(IR) current dominance, respectively.
• Blocking K(IR) currents with Ba2+ depolarized the membrane potential to near -45 mV.
• Cells with larger K(IR) currents showed membrane potentials around -70 mV.

Conclusions:

• Both K(IR) and K(V) currents play crucial roles in determining the resting membrane potential of LPS-activated microglia.
• The balance and magnitude of K(IR) and K(V) currents dictate the specific membrane potential observed.
• These findings provide insights into the electrophysiological changes in activated microglia and their potential functional implications.