title: Primary afferent neurons containing calcitonin gene-related peptide but not substance P in forepaw skin, dorsal root ganglia, and spinal cord of mice.
abstract: In mice dorsal root ganglia (DRG), some neurons express calcitonin gene-related peptide (CGRP) without substance P (SP; CGRP(+) SP(-) ). The projections and functions of these neurons are unknown. Therefore, we combined in vitro axonal tracing with multiple-labeling immunohistochemistry to neurochemically define these neurons and characterize their peripheral and central projections. Cervical spinal cord, DRG, and forepaw skin were removed from C57Bl/6 mice and multiple-labeled for CGRP, SP, and either marker for the sensory neuron subpopulations transient receptor potential vanilloid type 1 (TRPV1), neurofilament 200 (NF200), or vesicular glutamate transporter 2 (VGluT1). To determine central projections of CGRP(+) SP(-) neurons, Neurobiotin (NB) was applied to the C7 ventral ramus and visualized in DRG and spinal cord sections colabeled for CGRP and SP. Half (50%) of the CGRP-immunoreactive DRG neurons lacked detectable SP and had a mean soma size of 473 ± 14 μm(2) (n = 5); 89% of the CGRP(+) SP(-) neurons expressed NF200 (n = 5), but only 32% expressed TRPV1 (n = 5). Cutaneous CGRP(+) SP(-) fibers were numerous within dermal papillae and around hair shafts (n = 4). CGRP(+) SP(-) boutons were prevalent in lateral lamina I and in lamina IV/V of the dorsal horn (n = 5). NB predominantly labeled fibers penetrating lamina IV/V, 6 ± 3% contained CGRP (n = 5), and 21 ± 2% contained VGluT1 (n = 3). CGRP(+) SP(-) afferent neurons are likely to be non-nociceptive. Their soma size, neurochemical profile, and peripheral and central targets suggest that CGRP(+) SP(-) neurons are polymodal mechanoceptors.
authors.affiliation: Department of Anatomy and Histology, and Centre for Neuroscience, Flinders University, Adelaide, South Australia, 5001, Australia.
authors.forename: Garreth R
authors.initials: GR
authors.lastname: Kestell
authors.affiliation: Department of Anatomy and Histology, and Centre for Neuroscience, Flinders University, Adelaide, South Australia, 5001, Australia.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Anderson
authors.affiliation: Department of Anatomy and Histology, and Centre for Neuroscience, Flinders University, Adelaide, South Australia, 5001, Australia.
authors.forename: Jennifer N
authors.initials: JN
authors.lastname: Clarke
authors.affiliation: Department of Anatomy and Histology, and Centre for Neuroscience, Flinders University, Adelaide, South Australia, 5001, Australia.
authors.forename: Rainer V
authors.initials: RV
authors.lastname: Haberberger
authors.affiliation: Department of Anatomy and Histology, and Centre for Neuroscience, Flinders University, Adelaide, South Australia, 5001, Australia.
authors.forename: Ian L
authors.initials: IL
authors.lastname: Gibbins
mesh_terms: D000344:Afferent Pathways / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives / Q000378:metabolism; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D002452:Cell Count; D005260:Female; D005727:Ganglia, Spinal / Q000166:cytology*; D051379:Mice; D008810:Mice, Inbred C57BL; D016900:Neurofilament Proteins / Q000378:metabolism; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D011984:Sensory Receptor Cells / Q000378:metabolism*; D012867:Skin / Q000166:cytology* / Q000294:innervation; D013116:Spinal Cord / Q000166:cytology*; D013373:Substance P / Q000378:metabolism; D050916:TRPV Cation Channels / Q000378:metabolism; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism
chemical_list: D016900:Neurofilament Proteins; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; D050598:Vesicular Glutamate Transport Protein 1; C070614:neurobiotin; C051774:neurofilament protein H; D013373:Substance P; D001710:Biotin; D010751:Phosphopyruvate Hydratase; D015740:Calcitonin Gene-Related Peptide
keywords: AB_2313819; AB_2314983; AB_2315370; AB_2315546; AB_477257; CGRP; DRG; NF200; RRIDs: AB_572266; TRPV1; axonal tracing; nociception