Single-channel recording of TASK-3-like K⁺ channel and up-regulation of TASK-3 mRNA expression after spinal cord injury in rat dorsal root ganglion neurons

Single-channel recordings of TASK-1 and TASK-3, members of two-pore domain K⁺ channel family, have not yet been reported in dorsal root ganglion (DRG) neurons, even though their mRNA and activity in whole-cell currents have been detected in these neurons. Here, we report single-channel kinetics of the TASK-3-like K⁺ channel in DRG neurons and up-regulation of TASK-3 mRNA expression in tissues isolated from animals with spinal cord injury (SCI). In DRG neurons, the single-channel conductance of TASK-3-like K⁺ channel was 33.0±0.1 pS at -60 mV, and TASK-3 activity fell by 65±5% when the extracellular pH was changed from 7.3 to 6.3, indicating that the DRG K⁺ channel is similar to cloned TASK-3 channel. TASK-3 mRNA and protein levels in brain, spinal cord, and DRG were significantly higher in injured animals than in sham-operated ones. These results indicate that TASK-3 channels are expressed and functional in DRG neurons and the expression level is up-regulated following SCI, and suggest that TASK-3 channel could act as a potential background K⁺ channel under SCI-induced acidic condition.