The spinal dorsal horn is the first relay point relay point for somatosensory information arriving from peripheral sensory neurons. Complex circuits of local interneurons and projection neurons integrate this information and transmit the output to the brain, giving rise to the fundamental perceptions of pain, itch, touch, hot and cold. One major unanswered question with respect to the spinal dorsal horn is the following: Which specific types of dorsal horn neurons respond to distinct sensory stimuli, and what are the unique molecular and functional features of the responsive ensembles? To begin to answer this question, I propose to use use activity-dependent labeling coupled with electrophysiology and single-cell RNA-seq to identify and characetize the neuronal ensembles that mediate thermal pain and histamine-induced itch. In particular, I will use the novel calcium integrator CaMPARI to label neurons that respond to hot, cold and histamine in the spinal dorsal horn. Then, I will use the Patch-Seq method to perform electrophysiological recordings from the labeled neurons and finally capture each neuron’s RNA to profile its transcriptome. In this way, I expect to unveil the distinct neuronal populations that mediate these distinct sensory modalities. The insights gained from this project could lead to novel therapies for chronic pain and itch.