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H. P. Truong, R. Moon, M. Lii, D. Tran, M. Cho, K. Vanichsarn, T. Nguyen, M. Lim, J. Fallon, E. Wong; Mixed Motor and Sensory Functions in the V2 Branch of the Rat Trigeminal Nerve. Invest. Ophthalmol. Vis. Sci. 2010;51(13):15. doi: https://doi.org/.
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The human V3-branch of the trigeminal nerve is known to have mixed motor and sensory functions. Like many animals, the rat has contributed much to our knowledge of human anatomical function and has been heavily relied upon as prominent model for many human diseases.
Current anatomical knowledge of the rat suggests that the V2 branch of the trigeminal nerve has sole importance for sensory function. The purpose of the study is to investigate if the V2-branch of the trigeminal nerve of the rat has mixed motor and sensory functions similar to the V3-branch in humans.
The left trigeminal and facial nerves of two Sprague-Dawley rats were exposed to a neuronal retrograde tracer under general anesthesia. The left V2-branch of the trigeminal nerve was selectively exposed to a 4% Fluoro-Gold (FG) neuronal retrograde tracer for 45 minutes. The facial nerve was severed to prevent uptake of FG from the trigeminal nerve via greater petrosal and chorda tympani nerves. The proximal end of the facial nerve was exposed with 10% Fluoro-Ruby neuronal retrograde tracer solution using a micropipette, tied, and used as a control. The opposite, right side the face was used as a control. Horizontal sections of the brain, trigeminal nerve, and the superior portion of the spine were histologically evaluated under a fluorescent microscope.
Fluorescence of Fluoro-Gold was observed within the motor nuclei within the pons. Alternatively, presence of Fluoro-Ruby, injected into the left facial nerve, was observed in the left motor nuclei of the pons. The presence of the FG tracer within the trigeminal motor nuclei of the pons suggests a motor component within the nerve. There was no notable fluorescence of any neuronal tracers on the right hemisphere.
The results suggest that the V2 branch of the trigeminal nerve is associated with sensory as well as motor function. This shared characteristic with humans can enable the rat to be used as a model for further studying and understanding the V2 branch of the trigeminal nerve.
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