[Development and cell differentiation of the vestibulocochlear nuclei in cattle]

Based upon light- and electron microscopic examinations (50 embryos ranging from 1 to 53 cm crown-rump-length, CRL) the origin of the nuclei of the cranial nerve VIII is described with special regard to neurogenesis. The ventricular matrix lateral to the sulcus limitans represents the alar plate with its sensory areas. Up to 2.7 cm CRL migrating neurons from the vestibular nuclei can be detected, the bigger neuronal elements of which are the early formed lateral vestibular nucleus. From 6.7 cm CRL onward all nuclear groups of the vestibular nerve can be identified. At 1 cm CRL the recess plate represents the primordium of the cochlear nuclear complex. Identification of the definitive nuclei is possible at 3.8 cm CRL. Subsequently from 7.6 cm CRL onward the process of lamination can be observed in the dorsal cochlear nucleus. Due to the proceeding maturation the nuclei of the cranial nerve VIII correspond at 53 cm CRL topographically and cytologically to the characteristics of adult animals. Electron microscopic examinations are documenting characteristic features of cytogenesis of sensory neurons (vestibular nucleus) during early embryonic stages (2.5 cm and 3.6 cm CRL). At 2.5 cm CRL the elements exhibiting features of migrating neurons are predominating, whereas at 3.6 cm CRL an increased differentiation is typical for neurons localized in their ultimate position. At this stage synapses can be identified for the first time.