Introduction:

Potassium channels in oligodendrocytes, including inwardly rectifying (Kir), two-pore-domain (K2P), and voltage-gated (Kv) channels, are essential for potassium buffering, maintenance of myelin integrity, and central nervous system homeostasis (González et al., 2012). Disruption of oligodendroglial potassium conductance compromises potassium clearance, delays axonal recovery following repetitive firing, and is associated with seizures and motor dysfunction (Valerie et al., 2018). However, how distinct potassium channel populations are coordinated within oligodendrocytes, and whether this regulation differs between grey and white matter (GM, WM), remains poorly understood.

Methods:

Using whole-cell patch-clamp recordings in acute brain slices from C57BL/6 wild-type (WT) and TRPA1 global knockout (gKO) mice of both sexes, we assessed potassium conductance in mature oligodendrocytes (MOL) of the motor cortex and corpus callosum. Also, complementary immunohistochemical analyses across postnatal development in both sexes were used to examine associated changes in potassium channel and myelin protein expression.

Results:

We identify region-specific mechanisms of potassium channel regulation. Pharmacological blockade of Kir channels with barium (100 μM) significantly reduced potassium conductance in GM MOLs (ΔgK (%) = -30.7 ± 4.2, n = 11) but had minimal effects in WM MOLs (ΔgK (%) = -3.2 ± 3.0, n = 29; P < 0.0001), indicating differential reliance on Kir-mediated conductance across brain regions.

Previous studies suggested that the Transient Receptor Potential Ankyrin 1 (TRPA1) channel is expressed in oligodendrocytes and may influence potassium channel function (Hamilton et al., 2016). Consistent with this, activation of TRPA1 using multiple agonists, such as carvacrol, robustly inhibited oligodendroglial potassium conductance (caracrol evoked ΔgK (%) = -40.15 ± 2.16 %, n = 48).Moreover, TRPA1 global knockout mice exhibited a marked reduction in resting potassium conductance at postnatal days P12–P18 (WT gK (nS) = 6.77 ± 1.13, n = 8, gKO gK (nS) = 3.56 ± 0.48, n = 8; P = 0.0070), followed by an apparent compensation at P18–P25 (WT gK (nS) = 11.23 ± 1.36, n = 11, gKO gK (nS) = 10.77 ± 1.01, n = 7; P = 0.8117), when conductance returns to wild-type levels. Immunohistochemical analyses reveals a coincidental reduction in myelin basic protein (MBP) expression at P21 (P = 0.01, n = 5 each) that recovers by P30 (P = 0.817, n= 5 each). We found no significant sex differences.

Conclusion:

Ongoing work aims to determine how TRPA1 regulates oligodendroglial potassium channel expression and conductance in a region- and developmental stage-dependent manner, and how these mechanisms impact myelin structure and potassium siphoning. Together, these findings identify TRPA1 as a critical regulator of oligodendroglial potassium channel function and myelin stability, with potential relevance for activity-dependent myelin vulnerability in demyelinating disease.