title: Immunocytochemical evidence that most sensory neurons of the rat molar pulp express receptors for both glial cell line-derived neurotrophic factor and nerve growth factor.
abstract: Most pulpal afferent neurons have cytochemical features in common with the class of nociceptors that express neuropeptides and respond to NGF, while very few bind the plant lectin IB4, a widely used marker for the class of nociceptors that respond to the GDNF family of neurotrophic factors. The present study was undertaken to determine whether the GDNF receptor, GFRalpha-1, is expressed by pulpal afferents, and, further, to determine whether tooth injury evokes changes in expression of the GDNF and NGF receptors among pulpal afferents. The tracer, fluoro-gold (FG), was applied to shallow cavities in dentin of first and second maxillary molars. After 4 weeks, the molars of one side received a test injury consisting of a deeper cavity that exposed pulp horns. Animals were perfusion fixed 2 days later, and sections of the trigeminal ganglia were double immunostained with combinations of antibodies against GFRalpha-1, and TrkA. Under control conditions, GFRalpha-1 immunostaining was observed in 72% of neurons that projected to the molar pulp, TrkA in 78%, and immunostaining for both receptors was observed in 65% of pulpal afferents. Tooth injury evoked up-regulation of GFRalpha-1 expression (to 93%) and a slight down-regulation of TrkA expression (67%) among tooth afferents, while there was no discernable change in the proportion of pulpal afferents that expressed both TrkA and GFRalpha-1 (to 61%).
authors.affiliation: Department of Anatomy, University of Mississippi Medical Center, Jackson, 39216, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Yang
authors.forename: Jayne M
authors.initials: JM
authors.lastname: Bernanke
authors.forename: John P
authors.initials: JP
authors.lastname: Naftel
mesh_terms: D000818:Animals; D003731:Dental Caries / Q000378:metabolism / Q000503:physiopathology; D003782:Dental Pulp / Q000294:innervation*; D005260:Female; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000032:analysis; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors / Q000032:analysis*; D007150:Immunohistochemistry / Q000379:methods; D009414:Nerve Growth Factors / Q000032:analysis; D009475:Neurons, Afferent / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020800:Receptor, Nerve Growth Factor / Q000032:analysis*
chemical_list: D051100:Glial Cell Line-Derived Neurotrophic Factor; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors; D009414:Nerve Growth Factors; D020800:Receptor, Nerve Growth Factor