Kappa opioids inhibit spinal output neurons to suppress itch.

Itch is a protective sensation that drives scratching. Although specific cell types have been proposed to underlie itch, the neural basis for itch remains unclear. Here, we used two-photon Ca imaging of the dorsal horn to visualize neuronal populations that are activated by itch-inducing agents.

Identification of a convergent spinal neuron population that encodes itch.

Itch is a protective sensation that drives scratching. Although specific cell types have been proposed to underlie itch, the neural circuit basis for itch remains unclear. Here, we used two-photon Ca imaging of the dorsal horn to visualize the neuronal populations that are activated by itch-inducing agents.

Cell type-specific calcium imaging of central sensitization in mouse dorsal horn.

Allodynia is a state in which pain is elicited by innocuous stimuli. Capsaicin applied to the skin results in an allodynia that extends to a broad region beyond the application site. This sensitization is thought to be mediated by spinal networks; however, we do not have a clear picture of which spinal neurons mediate this phenomenon.

MrgprdCre lineage neurons mediate optogenetic allodynia through an emergent polysynaptic circuit.

Most cutaneous C fibers, including both peptidergic and nonpeptidergic subtypes, are presumed to be nociceptors and respond to noxious input in a graded manner. However, mechanically sensitive, nonpeptidergic C fibers also respond to mechanical input in the innocuous range, so the degree to which they contribute to nociception remains unclear. To address this gap, we investigated the function of nonpeptidergic afferents using the MrgprdCre allele.