Centrifugal fibres to the avian retina
About: This article is published in British Medical Bulletin.The article was published on 1970-05-01. It has received 152 citations till now.
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TL;DR: Findings suport the concept of intraaxonal retrograde movement of HRP, which was found in organelles within the axons of the optic nerve but not in the extracellular spaces of the retina.
Abstract: Retrograde transport of horseradish peroxidase (HRP) from the region of retinal genglion cell axon terminals back to the cell bodies has been studied by light and electron microscopy. After injection of HRP into the chick optic tectum, it was taken up by axon terminals and unmyelinated axons as well as by other processes and cell bodies of the outer tectal layers. Subsequently the HRP was obseved in vesicles, multivesicular bodies, cup-shaped organelles and small tubules within axons in the stratum opticum, optic tract, optic nerve and optic fiber layer of the retina with accumulation in the retinal ganglion cell bodies. Pinocytosis of extracellular HRP along the axon shaft was rare. After a short postinjection interval, HRP was found in organelles within the axons of the optic nerve but not in the extracellular spaces. After larger injections or longer postinjection intervals, extracellular HRP diffused from the injection site to the back of the eye, but none was found in the extracellular spaces of the retina; ganglion cells were the only cells of the retina which contained HRP product. HRP disappeared from the cell bodies 3–4 days after transport. These findings suport the concept of intraaxonal retrograde movement of HRP.
Within axons the vesicles carrying HRP frequently were partially or completely surrounded by a regualr array of microtubules. Doses of colchicine greater than 5–10 µ/eye administered 4 days before tectal injection of HRP interfered with the uptake and/or transport of HRP. HRP also moved in an anterograde direction in membrane-bound vesicles within the ganglion cell axons, although apparently more slowly and in smaller quantities than in the retrograde direction.
The localization of HRP in neurons of the isthmo-optic nucleus following intravitreal injections has also been studied. The marker enzyme was found in neuronal cell bodies 4 hours after injection, indicating a rate of retrograde transport of at least 84 mm/day in these neurons.
539 citations
TL;DR: The efferent connections of the ventral lateral geniculate nucleus of the albino rat and the cat have been studied using the autoradiographic method for tracing axonal pathways and no evidence could be found in either species for a projection from the LGNv to the visual cortex.
Abstract: The efferent connections of the ventral lateral geniculate nucleus (LGNv) of the albino rat and the cat have been studied using the autoradiographic method for tracing axonal pathways. Following the injection of 3H-proline or 3H-leucine into the LGNv of the rat, label transported in the rapid phase of axonal flow was found bilaterally in the olivary pretectal nuclei, the lateral terminal nuclei of the accessory optic system, and the ventral portion of the suprachiasmatic nuclei of the hypothalamus, and ipsilaterally in the rostrolateral portion of the superior colliculus. Since these regions are known to receive a direct projection from the retina, comparisons have been made of the distribution of silver grains in autoradiographs of each region following injections of 3H-proline into the eye and into the LGNv; in every nuclear region except the superior colliculus the grain distributions were found to overlap precisely and, in the suprachiasmatic nuclei there also appears to be a similarity in the relative intensity of the input to the nuclei on the two sides. In the superior colliculus, the retinal fibers end mainly within the more superficial laminae, whereas those from the LGNv are distributed mainly to the deeper layers where they overlap the projection from the striate and peristriate cortex. The LGNv has also been found to project to the zona incerta on the same side and to the contralateral LGNv, In the cat a similar set of projections to the lateral terminal nuclei of the accessory optic tract, the suprachiasmatic nuclei, and the pretectal areas of both sides has been found, together with a projection to the ipsilateral superior colliculus and the zona incerta of both sides. No evidence could be found in either species for a projection from the LGNv to the visual cortex.
424 citations
381 citations
01 Jan 1973
371 citations
TL;DR: Three aspects of the labelling pattern seen after the injection of 13 different radioactive amino acids into the pigeon optic tectum have been described.
Abstract: Three aspects of the labelling pattern seen after the injection of 13 different radioactive amino acids into the pigeon optic tectum have been described: The efferent projections of the optic tectum; the specific labelling of two pathways; and the dendritic organisation of tectal layer III neurons based on the retrograde and anterograde movement of label within these dendrites. Discrete injections of tritiated amino acid that involved all or only the superficial tectal layers suggested that layer III gave rise to the massive non-topographically organised and bilateral projections (fibers crossing within the decussato supraoptica ventrlis) upon the nuclei rotundus, subpraetectalis and interstitio-praetecto-subpraetectalis and to the ipsilaterally directed pathways terminating within the nuclei praetectalis, triangularis, subrotundus, dorsolateralis anterior thalami, posteroventralis and ventrolateralis thalami. Layer III neurons may also be the source of efferents to the posterior dorsolateral thalamus (the layer III pathway), the pontine grey and, bilaterally to the reticular formation and of the layer IV or tectal commisural pathway terminating within the contralateral tectal cortex. In contrast projections originating from layer II were generally topographically organised and terminated either within certain of the isthmic nuclei (n. isthmi pars parvocellularis, n. isthmo-opticus and n. semilunaris) or ran within layer I (layer I pathways) to end in the pretectum (griseum tectale) and ventral thalamus (n. ventrolateralis thalami, n. geniculatus, pars ventralis). A small projection from layer II upon the ipsilateral nucleus rotundus may also be present. Triated serine and tyrosine were found to be particularly effective in labeling perikarya as well as axons and terminals. The layer I pathway could be selectively labelled after tectal injections of 3H-GABA while the cell bodies of Ipc neurons were labelled in a retrograde fashion after tectal injections of 3H-glycine, serine or alanine. Intrinsic tectal labelling was found by correlation with Golgi material to reflect both anterograde and retrograde transport of label within dendrites of layer III cells. Anterograde movement of label indicated that the terminal portions of layer III cell dendrites ended in an orderly radial arrangement within sublayers IIb and IId, while the retrograde movement of label resulted in the labelin of layer III perikarya outside the injection field.
287 citations