Descending pathways from the brain stem to the spinal cord in some reptiles. II. Course and site of termination

Donkelaar, Hans J. ten

doi:10.1002/cne.901670404

Cited by 63 publications

(5 citation statements)

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“…A crossed rubrospinal tract is the major output of the RN. The trajectory of the rubrospinal tract described here is in agreement with previous descriptions of the rubrospinal pathway in reptiles (ten Donkelaar, 197613). As in mammals, the chelonian RN projects to the cerebellar nucleus and the LRN in the brainstem.…”

Section: The Reptilian Limb Premotor Networksupporting

confidence: 91%

“…Neuroanatomical studies have established the existence of numerous similarities between the pathways that constitute the reptilian rubrocerebellar system and its mammalian counterpart. Reptiles possess a well-developed red nucleus that projects heavily to the contralateral spinal cord (ten Donkelaar, 1976a). The major input to the reptilian red nucleus originates in the contralateral lateral cerebellar nucleus, which is homologous to the mammalian nucleus interpositus (Bangma et al, 1984).…”

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confidence: 99%

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Anatomical organization of the limb premotor network in the turtle (Chrysemys picta) revealed by in vitro transport of biocytin and neurobiotin

Sarrafizadeh¹,

Houk²

1994

J of Comparative Neurology

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The in vitro turtle brainstem-cerebellum preparation has been a valuable tool in the study of central motor programs. In the present study, we investigate the anatomical organization of the turtle rubrocerebellar limb premotor network and its sensory connections in vitro by combining the rapid anterograde and retrograde transport of neurobiotin and biocytin with the extended viability of the isolated turtle brainstem-cerebellum. These compounds retrogradely labeled soma, dendrites, and axons, and orthogradely labeled axons and, to a lesser extent, terminals. The chelonian red nucleus receives a dense input from the contralateral lateral cerebellar nucleus and projects heavily to the contralateral spinal cord. Rubral axons sparsely innervate the lateral cerebellar nucleus and project heavily to the lateral reticular nucleus. Lateral reticular axons heavily innervate the lateral cerebellar nucleus before terminating in the pars lateralis of the cerebellar cortex as mossy fibers. These prominent, recurrent loops among the lateral cerebellar nucleus, red nucleus, and lateral reticular nucleus constitute the turtle rubrocerebellar limb premotor network. Sensory inputs to the red nucleus originate in the contralateral dorsal column nuclei, the principal trigeminal nucleus, and the spinothalamic system. These sites project bilaterally to the lateral reticular nucleus. The lateral cerebellar nucleus receives a contralateral input from the dorsal column nuclei. The red nucleus projects sparsely to the dorsal column nuclei. The red nucleus also receives an ipsilateral descending projection from the suprapeduncular nucleus, located in the diencephalon, and an ascending input from the rostral rhombencephalic reticular formation. An ipsilateral descending pathway originating in the red nucleus is likely to be the rubro-olivary tract.

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Section: The Reptilian Limb Premotor Networksupporting

confidence: 91%

mentioning

confidence: 99%

Anatomical organization of the limb premotor network in the turtle (Chrysemys picta) revealed by in vitro transport of biocytin and neurobiotin

Sarrafizadeh¹,

Houk²

1994

J of Comparative Neurology

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“…Although the tecta of different vertebrate species appear to differ from one another in many profound ways, there is always one remarkable similarity: each gives rise to a crossed tecto-bulbar pathway. This efferent bundle has been found in all of the species studied to date, including species of elasmobranchs, ray-finned fishes, amphibians, reptiles, birds, and mammals (Herrick, 1948;Ariens Kappers et al, 1967;Smeets, 1981;Northcutt, 1983;Finkenstadt et al, 1983;Rubinson, 1968;Fos-ter& Hall, 1975;ten Donkelaar, 1976;Ulinski, 1977;Schroeder, 1981;Ebbesson, 1981;Welkeretal., 1983;Sereno, 1985;Sereno & Ulinski, 1985;Dacey & Ulinski, 1986a;Karten, 1965;Huerta & Harting, 1984). It is probably a primitive feature of the vertebrate tectum.…”

Section: Comparisons With Other Vertebratesmentioning

confidence: 99%

A light- and electron-microscopic investigation of the optic tectum of the frog, Rana pipiens, II: The neurons that give rise to the crossed tecto-bulbar pathway

Hughes

1990

Vis Neurosci

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The superficial layers of the frog's optic tectum, Potter's (1969) layers A-G, comprise a complex neuropil made up of many afferent axons, the somata of a few neurons, and many dendrites from the neurons located in the deeper layers. Different types of retinal axons are believed to terminate in different layers (Maturana et al., 1960; Kuljis & Karten, 1988; Sargent et al., 1989), but little is known about the relationships between each type of input and the dendrites of the deep tectal neurons that extend into these superficial layers. The present study used the method of retrograde transport of horseradish peroxidase to study the synaptic contacts on the dendrites of the neurons that give rise to the crossed tecto-bulbar pathway. These cells have apical dendrites that ascend through the superficial retino-recipient layers.The somata of the cells that give rise to the crossed tecto-bulbar pathway are located in the superficial half of layer 6, preferentially clustered along the caudal, lateral, and rostral margins of the tectum. The somata of these cells range from 8−30 ¼m in diameter. Their axons are large (2−4 ¼m in diameter) myelinated fibers that arise from either their somata or proximal dendrites. Their axons travel within the deep medullary layer to leave the tectum at the lateral margin. Their dendritic arbors extend obliquely through the superficial layers to reach layer B where they turn and extend within the layer for up to 0.5 mm. The somata of these cells receive only a scant synaptic input. In contrast, their dendrites receive input in every layer, but the nature of this input varies from layer to layer. Synaptic terminals that resemble retinal ganglion cell boutons contact the labeled dendrites in layers B, F, and G. This indicates that the dendrites may receive monosynaptic input from several types of retinal ganglion cells. Terminals with small, flattened vesicles also contact the dendrites of these cells in each layer. In layer F and below, the terminals with flattened vesicles constitute 15% of the contacts; above layer F they constitute only 5−8% of the contacts. Terminals with medium-sized, flattened vesicles also contact the dendrites of these cells in every layer and constitute a large proportion of their input (33−95%). The latter terminals resemble those that are often postsynaptic to retinal terminals.

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“…The pathways comprising the reptilian cerebellorubral system are summarized in Figure 1.4. Reptiles possess a well-developed red nucleus and rubrospinal tract that projects to the contralateral spinal cord (Ten Donkelaar, 1976). The primary input to the red nucleus is from the lateral cerebellar nucleus, homolog of nucleus interpositus, from the opposite side of the brain (Bangma et al, 1984).…”

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confidence: 99%

Sulforhodamine labeling of neural circuits engaged in motor pattern generation in the in vitro turtle brainstem-cerebellum

1992

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A fluorescent molecular probe was used in combination with a novel in vitro preparation to study spatial patterns of neural activity associated with motor pattern generation. The in vitro brainstem-cerebellum preparation takes advantage of the turtle's unusual resistance to anoxia to preserve the entire neural network that connects the cerebellum, red nucleus, and reticular formation. This preparation was bathed in a 0.01% solution of sulforhodamine while it was activated unilaterally by electrical stimulation of the dorsal quadrant of the spinal cord for 1 hr. Sulforhodamine is a small, sulfonated, highly charged fluorescent molecule that is taken up by endocytosis. To examine its distribution in the cerebellum and brainstem, coronal sections were prepared and viewed under epifluorescence illumination. Distinctive spatial patterns of labeling were associated with unilateral electrical stimulation of the in vitro network, suggesting that dye uptake was activity dependent. Blockade of uptake with altered magnesium and calcium concentrations indicated that single spike discharge evoked ortho- or antidromically was insufficient to induce dye uptake. Instead, sulforhodamine staining correlated with the presence of burst discharge that was recorded extracellularly from the red nucleus. Blockade of burst discharge with excitatory amino acid receptor antagonists prevented dye uptake in the red nucleus, the lateral cerebellar nucleus, and other structures that are known to be interconnected by recurrent anatomical pathways. These results suggest that sulforhodamine is internalized by intensely active neurons. The spatial distributions of label support the hypothesis that burst discharges in the turtle red nucleus are mediated by excitatory amino acid neurotransmitters and sustained by recurrent excitation in cerebellorubral synaptic pathways. Positive feedback in these recurrent pathways may provide an important driving force for the generation of motor programs that control limb movements.

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Descending pathways from the brain stem to the spinal cord in some reptiles. II. Course and site of termination

Cited by 63 publications

References 35 publications

Anatomical organization of the limb premotor network in the turtle (Chrysemys picta) revealed by in vitro transport of biocytin and neurobiotin

Anatomical organization of the limb premotor network in the turtle (Chrysemys picta) revealed by in vitro transport of biocytin and neurobiotin

A light- and electron-microscopic investigation of the optic tectum of the frog, Rana pipiens, II: The neurons that give rise to the crossed tecto-bulbar pathway

Sulforhodamine labeling of neural circuits engaged in motor pattern generation in the in vitro turtle brainstem-cerebellum

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