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Updated: Aug 29, 2026
Isolation and Whole-Cell Patch-Clamp Recording of Hippocampal Microglia from Adult Mice
Published on: September 27, 2024
Chemokine modulation of high-conductance Ca(2+)-sensitive K(+) currents in microglia from human hippocampi
1Department of Neurosurgery, Cellular and Molecular Physiology, Yale University, 333 Cedar Street, LSOG 228, New Haven, CT 06520-8082, USA. angelique.bordey@yale.edu
Abstract:
During acute pathological processes, microglia transform into an activated state characterized by a defined morphology and current profile, and are recruited to injury sites by chemokines. No information is available on the ion channels and the mode of action of chemokines in microglia in brain slices from humans with a chronic pathology. Thus, patch-clamp recordings of microglia were performed in hippocampal slices from seven patients who underwent surgery for pharmaco-resistant epilepsy. Cells were identified as microglia by positive labelling with fluorescein-conjugated tomato lectin before recording. All the recorded cells had an ameboid morphology characteristic of activated microglia. However, they had a high input resistance (3.6 G omega), a zero-current resting potential of -16 mV, and lacked Na+ currents, inwardly rectifying and delayed rectifying K+ currents such as non-activated microglia. Importantly, recorded cells expressed Ca2+-sensitive outward currents that activated at 0 mV with non-buffered intracellular Ca2+ and were sensitive to 1 mm tetraethylammonium (TEA). The estimated single-channel conductances were 187 pS in cell-attached and 149 pS in outside-out patches, similar to those of high-conductance Ca2+-dependent K+ channels. The chemokine MIP1-alpha increased whole-cell outward current amplitudes measured at +60 mV by a factor of 3.3. Thus, microglia in hippocampi from epileptic patients express high-conductance Ca2+-dependent K+ channels that are modulated by the chemokine MIP1-alpha. This modulation may contribute to the migratory effect of MIP1-alpha on microglia.
Insights
Microglia in epilepsy patients exhibit unique ion channel properties, expressing calcium-dependent potassium channels. The chemokine MIP1-alpha modulates these channels, potentially influencing microglial migration in chronic brain conditions.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglia adopt an activated state during acute inflammation, characterized by morphological and ionic changes, and are guided by chemokines.
- Limited data exists on ion channel function and chemokine action in microglia within human brain slices affected by chronic pathology.
Purpose of the Study:
- To investigate the ion channel characteristics and chemokine responses of microglia in hippocampal slices from human patients with chronic epilepsy.
- To elucidate the specific ion channels present and their modulation by chemokines in activated microglia in a chronic disease context.
Main Methods:
- Patch-clamp recordings were performed on microglia identified by lectin labeling in hippocampal slices from epilepsy patients.
- Electrophysiological properties, including resting potential, input resistance, and specific ion currents (Na+, K+, Ca2+-sensitive), were analyzed.
- The effect of the chemokine MIP1-alpha on microglial currents was assessed.
Main Results:
- Microglia in epileptic hippocampi displayed an ameboid morphology but lacked typical Na+ and K+ currents found in non-activated microglia.
- These activated microglia expressed Ca2+-sensitive outward currents, consistent with high-conductance Ca2+-dependent K+ channels.
- The chemokine MIP1-alpha significantly increased the amplitude of these outward currents.
Conclusions:
- Human epileptic microglia possess distinct electrophysiological profiles, notably expressing Ca2+-dependent K+ channels.
- Chemokine MIP1-alpha modulates these channels, suggesting a role in microglial migration and response within the epileptic brain.
- These findings offer insights into microglial function in chronic neurological disorders.
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