Afferent and efferent connections of the cerebellum of a salmonid, the rainbow trout (Oncorhynchus mykiss): A tract‐tracing study

Abstract

The connections of the cerebellum of the rainbow trout were studied by experimental methods. The pretectal paracommissural nucleus has reciprocal connections with the cerebellum. Three additional pretectal nuclei project to both the corpus and valvula cerebelli, and seem to receive cerebellar afferents. A large number of cells of the lateral nucleus of the valvula project to wide regions of the cerebellum, including the valvula, the corpus, the granular eminences, and the caudal lobe, whereas the contralateral inferior olive and scattered reticular cells project only to the corpus and valvula cerebelli. Afferents to the corpus were also observed from the ventral tegmental nucleus, the "paraisthmic nucleus," the perilemniscal nucleus, the central gray, and the octavolateral area. Valvular afferents were also observed from the torus semicircularis and the midbrain tegmental areas. In most cases of cerebellar application, labeled fibers were seen in the thalamus, the pretectum, the torus longitudinalis and torus semicircularis, the nucleus of the medial longitudinal fascicle, and midbrain and rhombencephalic reticular areas. From the corpus cerebelli some fibers also project to the posterior tubercle and the hypothalamus. Moreover, the granular eminences project to the cerebellar crest. DiI application to most of the areas showing labeled fibers after cerebellar tracer application led to the labeling of characteristic eurydendroid cells, mainly in the valvula cerebelli and the caudal lobe. A few putative eurydendroid cells were labeled from the octavolateralis regions. These results in a teleost with a generalized brain indicate several differences with respect to the cerebellar connections reported in other teleost fishes that have specialized brains.

Distribution of glycine immunoreactivity in the brain of the Siberian sturgeon (Acipenser baeri): Comparison with γ-aminobutyric acid

“…Unlike the case in the sea lamprey, the Gly-ir cells of the MON exhibit a typical Purkinje-like cell morphology, which is similar to that of the ''crest cells'' reported with Golgi methods in Acipenser rubicundus (Johnston, 1898). Experimental studies also reveal similar cells in the DON of the paddlefish (Hofmann et al, 2002) and in the MON of the brown trout and other teleosts (see Folgueira et al, 2006). These cells are the efferent neurons of lateral line nuclei in chondrosteans (Hofmann et al, 2002;Huesa et al, 2003), so the present results indicate that some crest cells are inhibitory glycinergic, which has not previously been reported in other fishes.…”

Immunohistochemical distribution of calretinin and calbindin (D‐28k) in the brain of the cladistian Polypterus senegalus

“…However, there are no experimental studies of the bichir cerebellum that may confirm this possibility. Although the homonymous nucleus of teleosts projects to the cerebellum (Folgueira et al, 2006), it does not contain CR-ir neurons (Castro et al, 2006b). This suggests either that CR expression was not conserved in the lateral valvular nucleus in ray-finned fish lineages, or that this bichir CR-ir nucleus is not homologous to the teleost lateral valvular nucleus.…”

Development of the cerebellum and cerebellar neural circuits

“…In the granule cell layer, synaptic interactions occur among mossy fibers, granule cells, and Golgi interneurons in the cerebellar glomeruli. Eurydendroid cells are located in the vicinity of the Purkinje cell layer, contact Purkinje cell axons, and send their axons through the granule cell layer to different areas outside the cerebellum in teleost (Murakami and Morita, 1987;Folgueira et al, 2006;Ikenaga et al, 2006).…”