Movie by Beatriz Torrez, PhD student in the Olsen Lab
Brain slice electrophysiology allows one to study a synapse or neural circuit in isolation. One can focus on the activity of a single cell, synapse, or even channel, and monitor its excitability or lack thereof. While astrocytes are considered to be non-excitable cells, they are critical at the synapse because that is where their perisynaptic astrocyte processes allow them to buffer ions and neurotransmitters, among other things. So they can still respond to electrical activity in the brain.
In an active synapse where action potentials are firing, the release of K+ ions into the extracellular space happens during the repolarization phase of the action potential. This K+ needs to get cleared in a rapid and efficient matter, otherwise abnormal discharges and a spreading depression may occur. Astrocytes express Kir4.1 channels and are very leaky cells, their Kir4.1 channels allow them to remove excess extracellular K+ and move it to regions of lower K concentration. This K buffering is also known to be coupled to astrocytic glutamate uptake. I can monitor this activity and more using electrophysiology – which can be a pretty stressful thing to tackle. Hopefully this ASMR is relaxing to those who enjoy the art of electrophysiology in a lab.