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Published January 6, 2005 | Supplemental Material
Journal Article Open

Topographically Distinct Epidermal Nociceptive Circuits Revealed by Axonal Tracers Targeted to Mrgprd


The brain receives sensory input from diverse peripheral tissues, including the skin, the body's largest sensory organ. Using genetically encoded axonal tracers expressed from the Mrgprd locus, we identify a subpopulation of nonpeptidergic, nociceptive neurons that project exclusively to the skin, and to no other peripheral tissue examined. Surprisingly, Mrgprd+ innervation is restricted to the epidermis and absent from specialized sensory structures. Furthermore, Mrgprd+ fibers terminate in a specific layer of the epidermis, the stratum granulosum. This termination zone is distinct from that innervated by most CGRP+ neurons, revealing that peptidergic and nonpeptidergic epidermal innervation is spatially segregated. The central projections deriving from these distinct epidermal innervation zones terminate in adjacent laminae in the dorsal spinal cord. Thus, afferent input from different layers of the epidermis is conveyed by topographically segregated sensory circuits, suggesting that at least some aspects of sensory information processing may be organized along labeled lines.

Additional Information

© 2005 by Elsevier Inc. Under an Elsevier user license. Received: September 13, 2004; Revised: November 1, 2004; Accepted: November 23, 2004; Published: January 5, 2005. We thank Allan Basbaum, Xinzhong Dong, and Richard Koerber for helpful discussions; Liching Lo for Figure 2A; Gaby Mosconi, Jung Sook Chang, and Monica Martinez for technical assistance; Nirao Shah for providing PLAP and ACN constructs; Shirley Pease and Jade Wang for performing blastocyst injections; and Jean Edens for help with electron microscopy. Supported in part by NIH grant NS34692 to F.L.R. D.J.A. is an Investigator of the Howard Hughes Medical Institute.

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