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Fast-conducting mechanonociceptors uniquely engage reflexive and affective pain circuitry to drive protective

Karina Lezgiyeva1,2, Jingyi Liu1,2, Karen Nguyen1,2

  • 1Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115.

Biorxiv : the Preprint Server for Biology
|November 26, 2025
PubMed

Insights

Researchers identified specific high-threshold mechanoreceptors (HTMRs) as key pain-sensing neurons. These Aδ-HTMRs are crucial for detecting damaging stimuli and initiating rapid protective withdrawal reflexes, offering new analgesic targets.

Area of Science:

  • Neuroscience
  • Pain Research
  • Sensory Biology

Background:

  • Nociceptors are critical for detecting harmful stimuli and initiating pain responses.
  • Identifying specific nociceptor subtypes is essential for understanding pain mechanisms and developing targeted therapies.

Purpose of the Study:

  • To identify genetically defined nociceptor populations responsible for pain behaviors using optogenetic activation.
  • To investigate the physiological, morphological, functional, and synaptic properties of identified nociceptor subtypes.

Main Methods:

  • Optogenetic activation screen to identify nociceptor populations.
  • Electrophysiological recordings and morphological analysis of identified neurons.
  • Investigation of central projections and synaptic connections in the spinal cord.

Main Results:

  • Smr2Cre- and Bmpr1bCre-labeled Aδ high-threshold mechanoreceptors (HTMRs) were identified as key nociceptors.
  • Aδ-HTMRs are activated by intense mechanical stimuli and are necessary for protective withdrawal responses.
  • These neurons form direct synaptic connections with spinal cord projection neurons and mediate rapid limb withdrawal reflexes.

Conclusions:

  • Aδ-HTMRs are a distinct class of myelinated nociceptors with unique properties.
  • Their specific roles in pain detection and motor reflexes highlight their potential as targets for novel analgesic development.

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