Comparative Ion Channel Transcriptomes of NK1R and Somatostatin Neurons in the PreBötzinger Complex of the...

The preBötzinger complex is among the few neural circuits where selective elimination of a defined neuronal subpopulation is sufficient to destabilize a core autonomic function and can fatally impair breathing. Within this circuitry, neurons expressing the neurokinin-1 receptor (Tacr1/NK1R) and somatostatin (Sst) are critical subpopulations; Tacr1⁺ neurons respond to the neuropeptide substance P and are necessary for maintaining inspiratory rhythms, and ablation of Sst⁺ neurons results in apneas. To further dissect and analyze the specific roles of Tacr1⁺ and Sst⁺ cell types, we conducted a comprehensive transcriptomic analysis using single-nucleus RNA sequencing of the sampled preBötC tissue from neonatal C57BL/6 J mice. As respiratory rhythmogenesis is an inherently electrophysiological process, we focused on the ion channel transcriptomes of Tacr1⁺ and Sst⁺ populations as a first step towards resolving the molecular underpinnings of their distinct contributions to breathing. A balanced random forest classifier distinguished Tacr1⁺ from Sst⁺ neurons with higher accuracy, indicating a distinct and relatively homogeneous ion channel identity in Tacr1⁺ neurons. Differential expression analyses identified coordinated upregulation of Trpc5, Kcnc2, and Cacna2d2 genes in Tacr1⁺ neurons. Tacr1⁺ neurons further exhibited elevated expression of the NALCN channelosome subunits and selective enrichment of Htr2c and Adra1a neuromodulatory receptor genes. Together, these findings define a molecularly distinct ion channel composition in Tacr1⁺ neurons and imply convergent substance P-linked mechanisms: TRPC5-mediated I_CAN and NALCN-mediated sodium leak conductance supporting rhythmic inspiratory activity, providing a molecular framework for targeted interrogation of respiratory circuit function.