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

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 ICAN and NALCN-mediated sodium leak conductance supporting rhythmic inspiratory activity, providing a molecular framework for targeted interrogation of respiratory circuit function.