Hierarchical organization of mechano-nociceptive pathways revealed by activity labeling

Noxious mechanical stimuli give rise to distinct percepts, from sharp cutaneous pain to diffuse visceral discomfort, yet the nociceptor ensembles that underlie these differences remain poorly defined. We mapped the peripheral architecture of nociceptive signaling by combining in vivo activity labeling of pelvic nerve afferents with single-cell RNA sequencing. Noxious stimuli recruited diverse classes of mechano-nociceptors, but stimulus type exerted modest influence on the composition of activated ensembles. Instead, tissue identity imposed the dominant organizational structure: stimulation of cutaneous and deep pelvic tissues engaged distinct subsets of both myelinated and unmyelinated neurons, revealing a clear domain-level division. Within this architecture, we identified a bladder-innervating myelinated nociceptor subtype with distinctive molecular features, illustrating an additional layer of refinement. Functional imaging and anatomical tracing corroborated this multilevel organization. These findings reveal a hierarchical organization of peripheral mechanical pain encoding, in which mechano-nociceptor populations are differentially engaged according to tissue domain and organ context.