title: Excitatory superficial dorsal horn interneurons are functionally heterogeneous and required for the full behavioral expression of pain and itch.
abstract: To what extent dorsal horn interneurons contribute to the modality specific processing of pain and itch messages is not known. Here, we report that loxp/cre-mediated CNS deletion of TR4, a testicular orphan nuclear receptor, results in loss of many excitatory interneurons in the superficial dorsal horn but preservation of primary afferents and spinal projection neurons. The interneuron loss is associated with a near complete absence of supraspinally integrated pain and itch behaviors, elevated mechanical withdrawal thresholds and loss of nerve injury-induced mechanical hypersensitivity, but reflex responsiveness to noxious heat, nerve injury-induced heat hypersensitivity, and tissue injury-induced heat and mechanical hypersensitivity are intact. We conclude that different subsets of dorsal horn excitatory interneurons contribute to tissue and nerve injury-induced heat and mechanical pain and that the full expression of supraspinally mediated pain and itch behaviors cannot be generated solely by nociceptor and pruritoceptor activation of projection neurons; concurrent activation of excitatory interneurons is essential.
authors.affiliation: Departments of Anatomy and Physiology, University of California, San Francisco, San Francisco, CA 94158, USA.
authors.forename: Xidao
authors.initials: X
authors.lastname: Wang
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Derek
authors.initials: D
authors.lastname: Eberhart
authors.forename: Rochelle
authors.initials: R
authors.lastname: Urban
authors.forename: Karuna
authors.initials: K
authors.lastname: Meda
authors.forename: Carlos
authors.initials: C
authors.lastname: Solorzano
authors.forename: Hiroki
authors.initials: H
authors.lastname: Yamanaka
authors.forename: Dennis
authors.initials: D
authors.lastname: Rice
authors.forename: Allan I
authors.initials: AI
authors.lastname: Basbaum
mesh_terms: D000818:Animals; D016923:Cell Death / Q000235:genetics; D003072:Cognition Disorders / Q000209:etiology / Q000235:genetics; D004195:Disease Models, Animal; D005968:Glutamate Decarboxylase / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006930:Hyperalgesia / Q000235:genetics / Q000473:pathology; D007395:Interneurons / Q000502:physiology*; D037102:Lectins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D016761:Oncogene Proteins v-fos / Q000378:metabolism; D010146:Pain / Q000235:genetics* / Q000473:pathology*; D017288:Pain Threshold / Q000502:physiology; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D011537:Pruritus / Q000235:genetics / Q000473:pathology*; D011930:Reaction Time / Q000235:genetics; D011987:Receptors, Steroid / Q000172:deficiency / Q000235:genetics*; D011988:Receptors, Thyroid Hormone / Q000172:deficiency / Q000235:genetics*; D013126:Spinal Nerve Roots / Q000473:pathology*; D013373:Substance P / Q000378:metabolism
chemical_list: D037102:Lectins; C092882:Nr2c2 protein, rat; D016761:Oncogene Proteins v-fos; D011987:Receptors, Steroid; D011988:Receptors, Thyroid Hormone; D049452:Green Fluorescent Proteins; D013373:Substance P; D005968:Glutamate Decarboxylase; D010751:Phosphopyruvate Hydratase