Table 1.
K+ Channel Expression in Peripheral Somatosensory System
| K+ Channel Family | a-subunit | Species | Assay | Commentary | Ref. |
|---|---|---|---|---|---|
| Kv1 | Kv1.1 - 1.6 | Rat | RNase protection assay, RT-PCR | Kv1.1 and Kv1.2 mRNAs were highly abundant while Kv1.3 - 1.6 mRNAs were detected at lower levels in L4-L5 DRGs | [28, 32] |
| Kv1.1, Kv1.2, Kv1.4 | Rat | IHC, electrophys. | Kv1.1 and Kv1.2 were predominantly found in large DRG neurons; small-diameter DRG neurons predominantly (but not exclusively) expressed Kv1.4. IB4-positive neurons expressed mostly Kv1.4 | [31, 33] | |
| Kv2 | Kv2.1, Kv2.2 | Rat | RT-PCR, IHC, electrophys. | mRNA products were found in the whole ganglion lysates and immunoreactivity found in cultured small neurons | [32, 35] |
| Kv2.1, Kv2.2 | Rat | IHC, in situ hybridization | Kv2.1 and Kv2.2 immunoreactivity and mRNA products were detected in DRG neurons of all sizes | [36] | |
| Kv3 | Kv3.1, Kv3.2, Kv3.5 | Rat | RT-PCR | mRNA products were found in the whole ganglion lysates | [32] |
| Kv3.4 | Rat | IHC | Kv3.4 expression was found mainly in C fibres (including axons, cell bodies and central terminals) | [38] | |
| Kv4 | Kv4.1, Kv4.2, Kv4.3 | Rat | RT-PCR | mRNA products were found in the whole ganglion lysates | [32] |
| Kv4.1, Kv4.3 | Rat | RT-PCR, IHC, electrophys. | mRNA and immunoreactivity of Kv4.1 and 4.3 (but not Kv4.2) was detected in small DRG neurons | [39] | |
| Kv4.1, Kv4.3 | Rat | In situ hybridization, IHC | mRNA products and immunoreactivity of Kv4.1 and 4.3 (but not Kv4.2) were detected. Kv4.3 was found mostly in small neurons while Kv4.1 in neurons of all sizes | [40] | |
| Kv4.3 | Rat | IHC | Kv4.3 expression was found mainly in non-peptidergic nociceptors | [38] | |
| Kv7 | Kv7.2, Kv7.3, Kv7.5 | Rat | RT-PCR, IHC, Electrophys. |
Detection of mRNA and immunoreactivity of Kv7.2, Kv7.3 and Kv7.5 in cultured DRG neurons of all sizes. M-like currents were recorded from small DRG neurons | [44] |
| Kv7.2 | Rat | RT-PCR, IHC, electrophys. | Kv7.2 was found to be predominantly expressed in small nociceptive neurons and unmyelinated fibres. M-like currents were recorded from acute DRG slices from adult rats | [45] | |
| Kv7.2 | Rat | IHC, electrophys. | Kv7.2 immunoreactivity was reported in skin terminals and afferents of Ad and C fibres. M current activity in the fibres was confirmed electrophysiologically | [48] | |
| Kv7.2 | Rat | IHC | Kv7.2 immunoreactivity was enriched in the nodes of Ranvier of myelinated fibres | [49, 50] | |
| Kv7.2, Kv7.3, Kv7.5 | Rat, mouse | IHC | Kv7.2 was found predominantly expressed in large DRG neurons and in the nodes of Ranvier of myelinated fibres; Kv7.3 was found in the nodes as well. Kv7.5 immunoreactivity was found predominantly in small neurons | [46] | |
| Kv7.2, Kv7.3, Kv7.5 | Rat | IHC, electrophys. | Expression of Kv7.2, Kv7.3 and Kv7.5 was found in the peripheral terminals of the aortic depressor nerve (nodose ganglion neurons). Kv7.2 was found in un-myelinated C fibres | [57] | |
| Silent Kvs | Kv8.1, Kv9.1, Kv9.3 | Rat | RT-PCR, IHC, electrophys. | mRNA products were found in the whole ganglion lysates and immunoreactivity for Kv9.1 and 9.3 was found in cultured small neurons | [35] |
| Kv9.1 | Rat | IHC, in situ hybridization | Kv9.1 immunoreactivity was detected in predominantly large, myelinated DRG neurons | [36] | |
| K2P | TASK-1, TASK-3, TREK-1, TRAAK, TWIK-1 | Rat | In situ hybridization | mRNA products were found in various subpopulations of DRG neurons. TWIK-1 was more abundant in large neurons | [63] |
| K2P | TRESK, TRAAK, TREK-2, TWIK-2, TREK-1, THIK-2, TASK-1, TASK-2, THIK-1, TASK-3 | Rat | RT-PCR | Whole DRG lysates were analysed for K2P expression, the mRNA abundances were found to follow the order of TRESK > TRAAK > TREK-2 = TWIK-2 > TREK-1=THIK-2 >TASK-1>TASK-2 > THIK-1 = TASK-3 | [64] |
| TREK-2, TRESK, TREK-1, TREK-2, TRAAK |
Rat | Correlative single-channel analysis, RT-PCR | TREK-2 and TRESK were found to underlie the majority of background K+ conductance in small- and medium-size DRG in culture | [65] | |
| TREK-1 | Mouse | IHC | TREK-1 immunoreactivity was abundant in DRG sections, small- and medium-sized neurons were stained predominantly | [68] | |
| TASK-1, TASK-2, TASK-3 | Rat | IHC | Expression of three TASK subunits in subpopulations of small- and medium-diameter DRG neurons have been characterized | [160] | |
| KATP | Kir6.1, Kir6.2, SUR1, SUR2 | Rat | RT-PCR, IHC, western blot | Kir6.1, Kir6.2, SUR1 and SUR2 mRNA products were found in whole DRG lysates; protein expression for all but Kir6.1 was confirmed by western blot and immunohistochemistry in subpopulation of neurons of various sizes | [74] |
| Slo | Slo1, rb2 | Rat | RT-PCR, electrophys. | Presence of Slo1/rb2 channels in small-diameter DRG neurons has been verified by correlative patch clamp analysis; rb2 expression was confirmed by RT-PCR from whole ganglion lysates | [78] |
| Slo2.1, Slo2.2 | Rat | RT-PCR, electrophys. | KNa currents were recorded in medium-size DRG neurons, presence of Slo2.1, Slo2.2 mRNA was confirmed by RT-PCR from whole ganglion lysates | [81] | |
| Slo2.2 | Rat | IHC, electrophys. | Slo2.2 immunoreactivity and KNa currents were found in DRG neurons of all sizes (≈90% of all neurons) | [80] |
IHC, immunohistochemistry.