Deletion of KCNQ2/3 Potassium Channels Enhances the Response of Airway Vagal Sensory Nerves to GPCR, But Not Ionotropic Receptor Activation

The KCNQ/K V 7/M-channel is a crucial intrinsic regulator of neuronal excitability. We have recently developed and validated a Pirt -driven sensory neuron Kcnq2 and Kcnq3 double knockout ( Kcnq2/3 -KO) mouse model, and demonstrated that the lack of KCNQ2 (K V 7.2) and KCNQ3 (K V 7.3), the two major α-subunits of M-channels in mouse nodose neurons, enhanced the action potential (AP) firings in response to electrically induced sustained depolarization. In this study, we aimed to determine whether the KCNQ2/3 channels play a role in inflammatory mediators-induced activation of vagal sensory neurons at the levels of cell soma located in the nodose ganglia and nerve endings terminating in the lungs. Inflammatory mediators activate the vagal nociceptive neurons by binding to either ionotropic or metabotropic receptors to initiate membrane depolarization and AP discharges. Here we examined the effects of KCNQ2/3 channel deficiency on the response of nodose nociceptive neurons to α,β-methylene ATP (α,β-mATP), an analogue of ATP that opens the ionotropic P2X2/3 channels, and to TFLLR, an agonist of the G q -coupled protease-activated receptor 1. In our ex-vivo mouse trachea-lungs-vagus nerve preparation, application of a bolus of α,β-mATP or TFLLR via trachea to the receptive field in the lungs evoked AP firings at the nociceptive C-fiber endings, which were recorded using an extracellular microelectrode positioned in the nodose ganglion and near the soma of the corresponding C-fibers. Knockout of KCNQ2/3 channels did not alter the response of bronchopulmonary C-fibers to α,β-mATP (at 0.1, 1 and 10 μM), with 10μM α,β-mATP evoking 131±25 (n=11) and 100±18 (n=10) APs for littermate control and Kcnq2/3 -KO fibers, respectively (p>0.05). The AP discharges in response to TFLLR (3, 10 and 30μM) were, however, significantly enhanced in Kcnq2/3 -KO nodose nociceptors (n=8) compared to littermate controls (n=10, p<0.001). Perforated patch clamp recordings on isolated nodose C-fiber neurons revealed similar findings. Bath application of 10 μM α,β-mATP evoked AP firings in 5 out of 9 control and 4 out of 6 Kcnq2/3 -KO nodose neurons, with averaged AP numbers being 146±88 and 192±100, respectively (p=0.74). TFLLR at 10 µM evoked AP firings in 6 out of 9 Kcnq2/3 -KO nodose neurons (194±42 APs), but only in one out of 11 control neurons (39 APs). Further analyses of patch clamp recordings found that the rising rate of TFLLR-evoked membrane depolarization was much slower than that evoked by α,β-mATP in both control (0.31±0.09 vs. 4.8±0.8 mV/s, p<0.001) and Kcnq2/3 -KO nodose neurons (0.60±0.20 vs. 4.0±1.4 mV/s, p=0.008). The effectiveness of KCNQ2/3 channels in limiting slower depolarization-induced AP firings is consistent with their biophysical properties - slow activation and lack of inactivation. In conclusion, our results indicate that the KCNQ2/3-mediated M-channel is an effective intrinsic brake on the activation of vagal nociceptive afferents by inflammatory mediators signaling through metabotropic receptors. Supported by NIH grant R35HL155671. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.