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A. Masuda, T. Hayakawa, S. Kuwahara, S. Kanno, M. Seki, O. Mimura; Immnohistochemical Characterization of the Trigeminal Ganglion Neurons Innervating the Cornea . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5082.
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© ARVO (1962-2015); The Authors (2016-present)
The cornea is sensitive to nociseptive inputs and receives dense sensory innervations from the trigeminal ganglion, which also innervates the superior palpebra. Thus we investigated whether single neuron of the trigeminal ganglia provided collateral innervations to the cornea and the superior palpebra. In addition we attempted to characterize the neurons innervating the cornea by immunohistochemical labeling with nociseptive related neuropeptides or neurotransmitters, such as calcitonin gene–related peptide (CGRP), transient receptor potentiated vanilloid 1 (TRPV1), and substance P (SP).
To label the neurons innervating the cornea and the superior palpebra, we injected the retrograde tracer Fluoro–Gold (FG) into the cornea and the retrograde tracer Cholera toxin (CT) into the superior palpebra of the same animal. We also characterized the neurons innervating the cornea by retrograde tracer FG following its injection into the cornea or the superior palpebra, and immunohistochemical double–labeling with CGRP, TRPV1, SP.
Both retrogradely FG–labeled and CT–labeled neurons were located intermingled in the trigeminal ganglion. There were a few FG–labeled neurons innervating the cornea (about10%) double–labeled with CT. FG–labeled neurons innervating the cornea (about 25 µm) were smaller than CT–labeled neurons innervating the superior palpebra (about 35 µm). While, about 30% of the FG–labeled neurons innervating the cornea were double–labeled with CGRP, about 20% with TRPV1, and about 10% with SP. About 5% of the FG–labeled neurons innervating the superior palpebra were double–labeled with CGRP, about 10% with TRPV1, and about 3% with SP.
These results showed that the cornea and the superior palpebra received innervations mainly from different neurons of the trigeminal ganglia. In addition, the cornea was innervated by many characteristic sensory neurons containing nociceptive related neuropeptides or neurotransmitters in the trigeminal ganglia.
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