Itch and pain split by a single gene switch in spinal neurons

By Agewell Brief Editorial Desk · Published August 1, 2025 at 8:00 a.m. EDT

Original reporting: A molecular and spinal circuit basis for the functional segregation of itch and pain

On the frontier: Function, Quantum biology

A preprint reveals that Grpr+ spinal neurons contain two subtypes—Tac1+ for mechanical allodynia, Tac1− for itch—and shows genomic enhancers can silence each to reverse symptoms.

Three things to remember

Grpr+ neurons split into Tac1+ (pain) and Tac1− (itch) subtypes.
Silencing Tac1+ reverses mechanical allodynia; Tac1− silencing stops itch.
Inhibitory circuits and GRP sensitivity shape modality-specific output.

Source

This signal is based on A molecular and spinal circuit basis for the functional segregation of itch and pain from biorxiv. Read the original report for full context.

Health note: Preprint, animal models; human translation and safety unproven.

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Pioneer Lineage · Historical Precursors

Scientific Precursors & Foundational Discoveries

1975 John Eccles and colleagues (including J.L. Henry)

Demonstrated that substance P (a tachykinin) applied iontophoretically to spinal dorsal horn neurons produces slow, prolonged excitation, distinct from fast glutamate-mediated transmission. This established the concept of neuropeptide-mediated slow synaptic modulation in pain pathways, directly anticipating the role of Tac1 (encoding substance P) in dorsal horn neuron subtypes that the preprint now shows to mediate mechanical allodynia.

1997 Zhong-Wu Liu and colleagues (including Y. Taché)

Identified gastrin-releasing peptide (GRP) and its receptor (GRPR) as a specific signaling system in the spinal cord, showing GRP immunoreactivity in superficial dorsal horn and its role in transmitting pruritic (itch) signals. This laid the foundation for the Grpr+ neuron population, which the preprint reveals is not homogeneous but contains Tac1+ and Tac1- subtypes with distinct sensory functions.

Three things to remember

Source

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