TY - JOUR
T1 - Neurotrophin receptor expression in retrogradely labeled trigeminal nociceptors - Comparisons with spinal nociceptors
AU - Mosconi, T.
AU - Snider, W. D.
AU - Jacquin, M. F.
N1 - Funding Information:
Wetha kDnr M. Barbacid and Dr L. Reichardt for contributing the trkA riboprobe and antibod, y respectiv,ean dlR. yG eren fohisrinvaluable technical assistance. This research was supported by NIH Grants DE07734, NS17763, and NS33939 to M..FJ.
PY - 2001
Y1 - 2001
N2 - In situ hybridization for trkA mRNA in trigeminal ganglion neurons retrogradely labeled with FluoroGold from the mandibular incisor demonstrated limited expression of the high-affinity nerve growth factor (NGF) receptor in this presumptive nociceptor population. Immunocytochemistry using polyclonal anti-trkA antibodies confirmed this result and extended it to show low levels of trkA protein expression in afferents labeled from the cornea. Less than 10% of the cells innervating the incisor, and ∼15% of those innervating the cornea, were trkA-positive in adult and neonatal mice. This proportion is considerably lower than that observed in Dorsal Root Ganglion nociceptors, in which ∼80% in neonates and ∼40% in adults express trkA (Molliver and Snider, J Comp Neurol 381: 428-438, 1997). Presumptive trigeminal nociceptors were further identified on the basis of expression of Calcitonin gene related peptide. In the entire ganglion, ∼43% of the trkA-positive cells were CGRP-positive, and ∼44% of the CGRP-positive cells were trkA-positive. Most trkA-positive cells that were CGRP-negative were medium-to-large diameter, while most of those that were CGRP-positive but trkA-negative were small diameter. Only ∼5% of trkA-positive cells labeled from the incisor, and ∼10% from the cornea, were CGRP-positive. Approximately 15% of the corneal or pulpal afferent neurons expressed ret-immunoreactivity. These results suggest that trigeminal nociceptors differ from spinal nociceptors in several significant ways. Differences in neurotrophic requirements may be related to differences in target tissues, in embryonic origin of some trigeminal ganglion cells, or in the timing of down-regulation of trkA expression in trigeminal ganglion cells.
AB - In situ hybridization for trkA mRNA in trigeminal ganglion neurons retrogradely labeled with FluoroGold from the mandibular incisor demonstrated limited expression of the high-affinity nerve growth factor (NGF) receptor in this presumptive nociceptor population. Immunocytochemistry using polyclonal anti-trkA antibodies confirmed this result and extended it to show low levels of trkA protein expression in afferents labeled from the cornea. Less than 10% of the cells innervating the incisor, and ∼15% of those innervating the cornea, were trkA-positive in adult and neonatal mice. This proportion is considerably lower than that observed in Dorsal Root Ganglion nociceptors, in which ∼80% in neonates and ∼40% in adults express trkA (Molliver and Snider, J Comp Neurol 381: 428-438, 1997). Presumptive trigeminal nociceptors were further identified on the basis of expression of Calcitonin gene related peptide. In the entire ganglion, ∼43% of the trkA-positive cells were CGRP-positive, and ∼44% of the CGRP-positive cells were trkA-positive. Most trkA-positive cells that were CGRP-negative were medium-to-large diameter, while most of those that were CGRP-positive but trkA-negative were small diameter. Only ∼5% of trkA-positive cells labeled from the incisor, and ∼10% from the cornea, were CGRP-positive. Approximately 15% of the corneal or pulpal afferent neurons expressed ret-immunoreactivity. These results suggest that trigeminal nociceptors differ from spinal nociceptors in several significant ways. Differences in neurotrophic requirements may be related to differences in target tissues, in embryonic origin of some trigeminal ganglion cells, or in the timing of down-regulation of trkA expression in trigeminal ganglion cells.
KW - Cornea
KW - Immunocytochemistry
KW - In situ hybridization
KW - Incisor
KW - Mouse
KW - trkA
UR - http://www.scopus.com/inward/record.url?scp=0035659596&partnerID=8YFLogxK
U2 - 10.1080/01421590120089695
DO - 10.1080/01421590120089695
M3 - Article
C2 - 11794733
AN - SCOPUS:0035659596
SN - 0899-0220
VL - 18
SP - 312
EP - 321
JO - Somatosensory and Motor Research
JF - Somatosensory and Motor Research
IS - 4
ER -