Cerebellar afferent projection to the inferior colliculus of the mesencephalic tectum. An anterograde degeneration study in the rabbit.

Studies were conducted on twelve rabbits which were lesioned in various regions of the cortex and cerebellar nuclei. The survival time, in ten animals, was found 4 to 10 days and in one animal 375 days. In the twelfth rabbit further lesions were made in the fastigial nucleus, 380 days after multiple lesions of the posterior cerebellar region. Survival time, in this case, was 9 days. Frozen sections of the cerebellum and brain stem were impregnated according to the Nauta-Gygax modified method (NAUTA 1957, Fink-Heimer 1967, Loewy 1969) and the course and termination of the nerve fibres into the inferior colliculus of the mesencephalic tectum has been studied. Degenerative fibres in this region of the brain stem were seen only after lesion of the fastigial nucleus or of its efferent fibres. The nucleus fastigii project the fibres to the inferior colliculus nuclei on both sides in the ascending ramus of the uncinatus fasciculus. These fibres reach the inferior colliculus nuclei mainly on the contralateral side and, to a lesser degree, on the same side. Results of the studies are discussed in the light of the latest neurophysiological researches.

The medial geniculate body afferents from the cerebellum in the rabbit as studied with the method of orthograde degeneration.

The brain stems of 10 rabbits subject to operation of several lesions of cerebellar cortex and nuclei were examined. Survival time was 4 to 10 days. The course and termination of degenerating nerve fibres into the medial geniculate nuclei (MGN) of both sides were analyzed in frozen sections of the cerebellum and the brain stem impregnated according to various modifications of Nauta method. Degenerated nerve fibres in the MGN were found only when the fastigial nucleus of heterolateral side, or fibres originating in this nucleus were damaged. Cerebellofugal fibres run in two bundles to their termination spot in the magnocellular part of the medial geniculate nucleus. The first bundle separates from the main trunk of the uncinate fascicle, and running medially to the vestibular nuclei, terminates in the MGN after passing through the lateral lemniscus and the ventral lemniscal nucleus. The second bundle separates from the ascending branch of the uncinate fascicle and after passing through the dorsal lemniscal nucleus, also in composition of the lateral lemniscus, it terminates in the same region of the MGN.

The spinal cervical way of afferent innervation of the tongue motor apparatus. An experimental investigation in the dog.

The studies were performed on 24 young, adult dogs. In 16 of the animals sections were made of the descending ramus of the hypoglossal nerve and of the stem of the hypoglossal nerve at various levels: at the base of the skull (superior hypoglossectomy), proximally from the descending ramus (middle hypoglosectomy), and at the entrance to the tongue (inferior hypoglossectomy). Phantom operations were performed in 4 animals and material from 4 others (not operated on) was used for control purposes. The post-operative survival rate ranged from 10 to 29 days. In all 4 cases rostral spinal cervical ganglia were collected. In half of the cases the materials were stained with cresyl violet and further quantitative and qualitative studies of retrograde neuronal changes were performed. The remaining half of the material, prepared with Gomori method on acid phosphatase, was subject to statistical analysis of the degree of acid phosphatase activity. The increase or decrease in number of neurons of definite degree of activity was taken as an index of the increase or decrease of enzymatic activity. As a result of transection of the hypoglossal nerve and its descending ramus, in cresyl violet material, qualitative and quantitative degenerative changes were found in dorsal root ganglia C1 to C3 on the operated side. It was also found that corresponding to the tigrolytic changes in the neurons of the above mentioned ganglia there was an increase of activity for acid phosphatase. The same kinds of changes were found in the spinal ganglia C2 and C3 after transection of the hypoglossal nerve at the entrance to the muscles of the tongue. These results lead the authors to suggest that the tongue motor apparatus receives afferent innervation from neurons locates homolaterally in spinal ganglia C2 and C3.

[Afferents of vagus nerve to intercalary nucleus]. / Afférences du nerf vague an noyau intercalé

In 11 rabbits operations of intracranial transection of IXth and Xth cranial nerves and transections of vagal nerve on its several levels were performed. After survival 271-327 days karyometric investigations of neurons, astrocytes and oligodendrocytes contained in intercalary nuclei of both sides of medulla were performed. It was stated that after transection of the vagus nerve on the levels proximally to the arising of the recurrent laryngeal nerve the volume of cross-area of neurons and nuclei of astrocytes decreases on the operated side. The authors concluded that atrophic changes found in the intercalary nucleus may be probable of transsynaptic in character. It indicated, that intercalary nucleus receives afferents from the vagus nerve.