Afferent sources to the inferior olive and distribution of the olivocerebellar climbing fibers in cyprinids

Abstract

The inferior olive in teleosts is a major afferent origin to the cerebellum. However, inputs to the inferior olive remain largely unknown. The present study examined fiber connections of the inferior olive by tract-tracing methods in cyprinids. After tracer injections into the inferior olive, labeled somata were observed bilaterally in the pretectum, nucleus ruber, principal sensory trigeminal nucleus, descending trigeminal nucleus, inferior reticular formation, and cerebellar valvula. Principal sensory trigeminal and valvular afferents exhibited a clear contralateral preponderance, while afferents from the nucleus ruber were predominantly ipsilateral. Labeled somata were also seen ipsilaterally in the descending octaval nucleus, and contralaterally in the optic tectum, lateral funicular nucleus, cerebellar corpus, and inferior olive. A few somata were labeled in the inferior raphe. Climbing fibers terminated contralaterally in the ganglionic and molecular layers of the cerebellum, showing peculiar glomerular appearances. Labeled climbing fiber terminals were mainly distributed in the ventral region of cerebellar corpus, the medioventral region of lateral lobe of rostral cerebellar valvula, and the lateroventral region of medial lobe of cerebellar valvula in the present injection materials. Fiber connections of the inferior olive in teleosts thus appear quite similar to those in mammals.

Fiber Connections of the Caudal Corpus Cerebelli, with Special Reference to the Intrinsic Circuitry, in a Teleost (<b><i>Oreochromis niloticus</i></b>)

“…In turn, tracer applications into the GGL of the vcC resulted in labeled terminals in the GGL Reconstructed labeled single axons from the vcC formed beaded terminals in the GGL of the dcC, which were clearly different from terminals of climbing fibers that originate from the IO and terminate on PuC dendrites of the cerebellum. The climbing fiber terminals have been observed mainly in the ML as clusters of terminal boutons or complex helicoid configurations [Finger, 1983;Han et al, 2006;Xue et al, 2008]. Since the beaded terminals were present in the GGL (not in the ML), the labeled axons in the present study probably make synaptic contacts with cell bodies of EuC in the GGL of the dcC.…”

“…5A, 6B). Failure to label IO cells in these cases may have been due to our injections mainly into the superficial ML; climbing fibers terminate in the GGL and deep ML [Xue et al, 2008]. In the other 2 cases, a number of cerebello-petal nuclei such as ipsilateral AP, NPC, and NLV and contralateral IO were retrogradely labeled (data not shown) in addition to the intrinsic cerebellar labeling.…”

Comparative analysis of serotonin receptor (HTR1A/HTR1B families) and transporter (slc6a4a/b) gene expression in the zebrafish brain

“…It sends projections to the inferior olive and has reciprocal connections with the optic tectum and the cerebellum (Wullimann and Northcutt, 1989;Xue et al, , 2008. It may function to convey somatosensory and mechanosensory (lateral line) information as well as visual information.…”

Nucleus Ruber of Actinopterygians

“…Presumably different populations of neurons, which project to the nucleus isthmi (carp and Nile tilapia [Xue et al, 2001]), inferior olive (carp and goldfish [Xue et al, 2008]), and TO (carp [Luiten, 1981]; Nile tilapia [Sawai et al, 2000]), have been identified close to the spinal projection neurons of NRg. These populations have been regarded as parts of the NRg, since these neurons are present around the region of NRg.…”

“…As stated in the introduction, nucleus ruber of actinopterygians may control the movement of the pectoral fin, which is homologous to the forelimb of tetrapods. Terminations of cerebellar efferents in the NRg are in support of motor functions of the nucleus (ictalurids [Finger, 1978]; carp [Xue et al, 2008]). Uematsu and Todo [1997] reported that in the carp bilateral and unilateral rhythmical movements of the body and tail were elicited by electrical stimulation of the mesencephalic tegmentum, including 'nucleus ruber', suggesting involvement of the tegmentum in the control of swimming.…”