title: Chemical phenotypes of muscle and cutaneous afferent neurons in the rat trigeminal ganglion.
abstract: Retrograde labeling was combined with cytochemistry to investigate phenotypic differences in primary afferent neurons relaying sensory information from deep and superficial craniofacial tissues. Calcitonin gene-related peptide (CGRP), substance P (SP), somatostatin (SOM) immunoreactivity and isolectin IB4, and cholera toxin B (ChTB) binding were examined for trigeminal masticatory muscle and cutaneous afferent neurons. Somata labeled from muscle were larger than cutaneous afferent neurons. Muscle afferent neurons exhibited positive staining as follows: 22% CGRP, 5% SP, 0% SOM; 18% ChTB, 5% IB4. The somata of CGRP- and SP-positive muscle afferent neurons were smaller than that of the overall muscle afferent population. Size differences were not detected between IB4- or ChTB-binding muscle afferent neurons and the total muscle afferent population. The following distribution was found for cutaneous afferent neurons: 26% CGRP, 7% SP, 1% SOM, 26% ChTB, 44% IB4. Cutaneous afferent neurons positive for SP were smaller, while ChTB-binding cutaneous afferents were larger than the overall cutaneous afferent population. No size differences were found between cutaneous CGRP-, SOM-, or IB4-positive neurons and the total cutaneous afferent population. Target-specific differences exist for SOM and IB4. The percentage of cutaneous afferent neurons positive for SOM and IB4 exceeds that for SOM- or IB4-positive muscle afferents. The number of retrogradely labeled neurons never differed between sexes. The percentage of retrogradely labeled muscle afferent neurons that were CGRP-positive was greater in males than females. These data indicate the presence of phenotypic, target, and sex differences in trigeminal ganglion primary afferent neurons.
authors.affiliation: Department of Oral and Craniofacial Biological Sciences and Program in Neuroscience, University of Maryland at Baltimore, Baltimore, Maryland 21201, USA. ramba001@umaryland.edu
authors.forename: Ranjinidevi
authors.initials: R
authors.lastname: Ambalavanar
authors.forename: Masayuki
authors.initials: M
authors.lastname: Moritani
authors.forename: Ashley
authors.initials: A
authors.lastname: Haines
authors.forename: Tia
authors.initials: T
authors.lastname: Hilton
authors.forename: Dean
authors.initials: D
authors.lastname: Dessem
mesh_terms: D000818:Animals; D048429:Cell Size / Q000502:physiology; D005260:Female; D008297:Male; D018482:Muscle, Skeletal / Q000737:chemistry* / Q000166:cytology / Q000502:physiology; D009475:Neurons, Afferent / Q000737:chemistry* / Q000166:cytology / Q000502:physiology; D010641:Phenotype; D051381:Rats; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics; D012867:Skin / Q000737:chemistry / Q000166:cytology; D012668:Trigeminal Ganglion / Q000737:chemistry* / Q000166:cytology / Q000502:physiology