Nucleo-olivary projection

Fig. 101. Diagram of the projections of the dentate and interposed cerebellar nuclei (CN) and the mossy and climbing fiber recurrent circuits. The non-GABAergic projections of the nuclei divide in ascending (A and C) and descending (B) branches. The descending branch terminates in the nucleus reticularis tegmenti pontis (NRTP), one of the main sources of the mossy fiber collateral projection to the nuclei. The ascending branch terminates in the red nucleus (n. ruber), the nuclei of the mesodiencephalic junction MDJ, a relay in the recurrent cerebellomesencepho-olivary loop, and in the ventral tier nuclei of the thalamus (VA/VL). The GABAergic nucleo-olivary projection (2) terminates in the inferior olive (lO). Courtesy of Dr. T.J.H. Ruigrok.

THE GABAERGIC NUCLEO-OLIVARY PROJECTION NEURONS OF THE CEREBELLAR NUCLEI... 

The topography in the cerebellar nucleo-olivary projection has been studied in different mammalian species. The nucleo-olivary fibers from the interposed and lateral nuclei run in a separate tract, ventral to the brachium conjunctivum in cat (Legendre and Courville, 1987), rat (Cholley et al., 1989) and rabbit (Tan et al., 1995b). Fastigio-olivary... 

Fig. 164. The nucleo-olivary projection in the rat. Data from Ruigrok and Voogd (1990). Upper and lower block diagrams represent the cerebellar and vestibular nuclei, and the subdivisions of the inferior olive respectively. According to Ruigrok and Voogd (1990) the cerebellar nuclei and their olivary target nuclei can be considered as a continuum, stretching from the rostral medial cerebellar nucleus, projecting to caudal MAO, to the lateral vestibular nucleus, projecting to the dorsal fold of the DAO. DL = dorsolateral protuberance of the medial cerebellar nucleus DMC = dorsomedial cell column IntA = anterior interposed nucleus IntDL = dorsolateral hump IntP = posterior interposed nucleus lOD = dorsal accessory olive lODM = dorsomedial cell column lOM = medial accessory olive lOP = principal olive Lat = lateral cerebellar nucleus LVe = lateral vestibular nucleus Med = medial cerebellar nucleus VL = ventrolateral outgrowth.

The nucleo-olivary projection is not completely crossed. Some fibers from the dorsolateral hump, IP and the ventromedial lateral nucleus recross at the level of the inferior olive, and terminate in the ipsilateral DM, rostral MAO and ventral leaf of the PO respectively. Ipsilateral labelling was sparse or absent in other parts of the inferior olive. 

Projections from the vestibular nuclei terminate in subnuclei that do not receive a nucleo-olivary projection, such as the DMCC, the group beta and the central region (subnucleus b) of the caudal MAO in cat (Fig. 165) (Saint-Cyr and Courville, 1979 Gerrits et al., 1985a), opossum (Martin et al., 1980) and rat (Nelson and Mugnaini,... 

Dietrichs E, Walberg F (1981) The cerebellar nucleo-olivary projection in the cat. Anat. Embryoi, 162, 51-67. 

Ruigrok TJH, Voogd J (1990) Cerebellar nucleo-olivary projections in the rat An anterograde tracing study with Phaseolus vu/gam-Leucoagglutinin (PHA-L). J. Comp. Neurol, 298, 315-333. 

Afferent systems of the inferior olive have been reviewed by Brodal and Kawamura (1980) for the cat and by Martin et al. (1980) for the opossum. For the rat the tabulated summary of its afferent connections in the paper of Brown et al. (1977) and the review by Flumerfelt and Hryccyshyn (1985) are useful. Afferent systems of the inferior olive can be subdivided into three groups (1) the GABAergic nucleo-olivary and vestibulo-olivary projections (2) the monoaminergic and cholinergic projections to the inferior olive (3) the specific projections from the spinal cord, certain brain stem nuclei and the cerebral cortex will not be considered in this chapter. Their neurotransmitters are not known. 

The nucleo-olivary and vestibulo-olivary projections The GABAergic afferents of the inferior olive... 

Dietrichs E, Walberg F (1985) The cerebellar nucleo-olivary and olivo-cerebellar nuclear projections in the cat as studied with anterograde and retrograde transport in the same animal after implantation of crystalline WGA-HRP. II. The fastigial nucleus. Anat. Embryoi. 173, 253-261. 

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