Experimental morphological studies on central projection of snout proprioceptive afferents in moles

Abstract

It had been provedt hat the facial nerve of molesc ontaineda proprioceptivefi ber element. But its projectiona reas remainedu nknown. They were here investigatedb y the Nauta method and I-IRPla bellingm ethoda nd by electronm icroscopy. The proprioceptivaef ferentf ibers, a fter entering the pons, are dividedr ostro-caudallyi nto the shorter ascending and the longer descending roots, both running closely dorsal to the trigeminals pinal tract nucleus (TSTN. ) The ascending root takes the vertical course adjacently dorsal to the TSTN, giving off manyt erminalf iberst o it and the other dorso-medialp ontine nuclei. At the levelo f the inner genu, it turns medially to meet the facial motor root and runs to the facial motor nucleus cells bilaterally. The descendingro ot takes the vertical coursec audallya t least downt o C3, g iving off many terminal fibers to the TSTN, and the nuclei of IXth, Xth and XIIth cranial nerves. At the level of the spinal cord, the root is divided into two and they descend bilaterally through the posterior fasciculi, p rojectingt o the posteriora nd anteriorh ornc ells. Fromt hese results, it can bee mphasizetdh at the snoutp roprioceptivfeib ersp rojectb ilaterally to the facialm otorn ucleusa nd the cervicalm otorn eurons, t he latter composinga mono-synaptic reflex system between the snout muscles and neck muscles