Neuronal bifurcated projections from the trigeminal ganglion to the
infraorbital nerve and transverse sinus and their correlation with the
oxytocin receptor and CGRP
Abstract
Abstract Our principal was to demonstrate the convergence of the
trigeminal ganglion population from the transversal meningeal sinus and
the infraorbital nerve. Recent data suggest that some trigeminal
ganglion cells simultaneously send neuronal projections to craniofacial
structures via the V1 and V2 trigeminal branches; however, no conclusive
evidence exists. Hence, immunohistological assays using retrograde
neural tracers injected at the V1 (meningeal dura mater at the
transverse sinus level; true-blue, (TB) and V2 (infraorbital nerve;
fluoro-gold, (FG) branches were performed to test the hypothesis
regarding the convergence of different trigeminal branches to one
trigeminal ganglion cell. Besides, bifurcated labeled sensory trigeminal
nerves were quantified in adult (60 days old) and young rats (30 days
old). The correlation between oxytocin receptor (OTR), calcitonin
gene-related peptide (CGRP), and IB4 was analyzed. Cells were labeled
concomitantly with FG and TB neuro tracers at the trigeminal ganglion.
Interestingly, young animals showed more labeled cells than did adult
rats. Triple-labeled neurons (i.e., CGRP/FG/TB and OTR/FG/TB) were found
in trigeminal ganglion cells, implying that CGRPergic fibers can be
modulated by OTR activation in meningeal or infraorbital nerve fibers.
These data support the contention that bifurcated trigeminal ganglion
cells simultaneously run via two trigeminal branches (V1 and V2).
Finally, the significant decrease in labeled ganglionic cells at 60 days
compared to rats 30 days old needs to be followed to understand the
developmental process of the orofacial system.