Papers of the Week

Glycinergic neurons regulate nociceptive and pruriceptive signaling in the spinal cord, and the identity and role of the glycine-regulated neurons are not fully known. Herein, we have characterized spinal glycine receptor alpha 3 () subunit-expressing neurons in -Cre female and male mice. -Cre(+) neurons express , are located mainly in laminae III‒VI, and respond to glycine. Chemogenetic activation of spinal -Cre(+) neurons induced biting/licking, stomping, and guarding behaviors, indicative of both a nociceptive and pruriceptive role for this population. Chemogenetic inhibition did not affect mechanical or thermal responses, but reduced behaviors evoked by compound 48/80 and chloroquine, revealing a pruriceptive role for these neurons. Spinal cells activated by compound 48/80 or chloroquine express , further supporting the phenotype. Retrograde tracing revealed that spinal -Cre(+) neurons receive input from afferents associated with pain and itch, and dorsal root stimulation validated the monosynaptic input. In conclusion, these results show that spinal (+) neurons contribute to acute communication of compound 48/80- and chloroquine-induced itch in hairy skin. Spinal glycinergic neurons regulate itch (pruriception), suggesting that components of the glycinergic system have great potential as drug targets to treat pruritus. Nonetheless, thus far, the pruriceptive roles of any of the glycine receptor (GLR) subunits have not been evaluated. Here, we successfully linked the -Cre populations to a pro-pruriceptive role in itch, indicating that GLRA3-expressing neurons may be a potential novel target for itch treatment. The spontaneous stomping and guarding behaviors observed from activating the -Cre populations are indicative of a role in sensory hypersensitivity and hence, raises questions regarding the hypersensitivity involvement of these populations for future investigations.