Understanding spinal neuropeptide signaling in itch

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PROJECT SUMMARY/ABSTRACT Chronic itch disorders are the primary reason for visits to dermatologists and have devasting effects on patient quality of life. Despite extensive research efforts, an effective treatment for chronic itch remains elusive, in part because the basic neural coding that underlies itch is poorly understood. The long-term goal of the investigator’s research program is to elucidate the neural mechanisms that underlie processing of itch input under normal and pathological conditions. Interestingly, one hallmark of chronic itch disorders is the upregulation of excitatory neuropeptides that drive itch – substance P (SP) and gastrin-releasing peptide (GRP) – within the spinal cord. However, the mechanism by which neuropeptides modulate spinal circuits to produce itch is unclear. To address this fundamental gap in knowledge, this proposal will investigate whether neuropeptides (SP and GRP) act in parallel with neurotransmitters (on the same targets) or if neuropeptide signaling diverges from neurotransmission (engage distinct targets), thereby reconfiguring spinal circuits. Specifically, the investigator will test the hypothesis that the itch-inducing neuropeptides SP and GRP act via divergent signaling to reconfigure neural circuits in acute and persistent itch. During the K99 Phase, she will learn and apply cutting- edge approaches that span from the neuron ultrastructural to population level. Aim 1 (K99) will compare spinal synaptic connectivity to neuropeptide connectivity using multiplexed electron microscopy. Aim 2 (K99) will identify the spinal networks activated by neuropeptide versus synaptic transmission from SP (and GRP) spinal neurons using two-photon Ca2+ imaging in combination with an ex vivo somatosensory preparation. A portion of the K99 phase will also be dedicated to learning to implement machine learning algorithms to detect and quantify mouse itch behaviors, and to career development activities such as gaining leadership and mentorship skills and presenting at conferences to expand the applicant’s professional network. Aim 3 (R00) will determine whether the SP and GRP signaling are required for the manifestation of aberrant spontaneous spinal cord activity (Aim 3A) and elevated itch behaviors (Aim 3B) associated with persistent itch using pharmacological inhibition strategies. These studies will leverage her new expertise in two-photon Ca2+ imaging and automated behavioral analysis pipelines developed during the K99 phase in combination with her strong background in rodent itch models. Together, these experiments will provide fundamental insights into neuropeptide signaling in spinal itch transmission and identify the necessity of spinal neuropeptide signaling in persistent itch. The success of this career award training plan, which includes activities for scientific and career development, will be aided by the scientific expertise, collaboration, and educational opportunities offered by the Pittsburgh Center for Pain Research. Completing this plan will prepare the applicant to lead an innovative research program as an independent investigator.