Ipsilateral retinal projections into the tectum during regeneration of the optic nerve in the cichlid fishHaplochromis burtoni: A dil study in fixed tissue (original) (raw)
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Journal of Neurobiology, 1992
The normal development of the retinal projection was studied in a bony fish with Dil. Between 5.5 and 10 days postfertilkation the contralateral retinal projection grows from the rostra1 pole of the tectum across its center. A maximum of 15 retinal fibers reaches the ipsilateral tectum. In 33-day-old juvenile animals, less than 15 ipsilateral fibers terminate in the entire tectum. Ipsilaterally projecting ganglion cells (maximal number = 20 cells) are scattered throughout the entire retina, and the location of ganglion cells in the retina and axonal terminations in the tectum display a large interindividual variability. This suggests that the small adult contingent of ipsilateral fibers in this bony fish develops without an initial exuberant ipsilateral retinal projection that is later pruned back. 0 1992 John Wile) & Sons, Inc.
Journal of Neurobiology, 1993
The development and regeneration of the ipsilateral retinopetal projection of the nucleus olfactoretinalis (NOR) in the cichlid fish Huplochromis burtoni was studied with 1,1 '-dioctadecyL3,3,3',3'-tetramethyI indocarbocyanine perchlorate ( DiI) in fixed tissue. Throughout development most NOR cells projected to the contralateral retina. Only an insignificant, transient elevation of a projection to the ipsilateral retina was found in a few animals; however, after severing the contralateral processes of NOR cells by either enucleation or nerve crush, many animals had significantly more NOR cells with a regenerated process to the ipsilateral retina. Nevertheless, within a few weeks of surgery, the number of animals with ipsilaterally projecting cells were reduced to control values. The transiently enhanced ipsilateral projections to the retina imply changes in the guiding mechanism after these operations and the existence of control mechanisms against unusual connections to the retina in this bony fish.
Brain Research, 1977
Following unilateral enucleation and optic nerve crush in goldfish, the remaining nerve regenerates and innervates both optic tecta. Approximately 5 ~ of the nerve fibers reach the ipsilateral optic tectum (IOT) via the ipsilateral tract at the chiasma. Comparable debris in both tracts was not sufficient to result in an IOT projection since when both nerves were crushed simultaneously the usual pattern was seen, i.e., each nerve innervated a contralateral optic tectum (COT). When the arrival of one nerve at the chiasma was delayed by staggering the nerve crushes, the nerve that first arrived at the chiasma partially innervated the IOT. In most instances the entire IOT was innervated, however, the stratigraphic distribution of fibers in the various tectal lamina was atypical.
NEURAL ACTIVITY IN THE REGENERATING OPTIC NERVE OF THE GOLDFISH
1. Retinal ganglion cells of one eye were axotomized in goldfish either by sectioning the contralateral optic tract or by ablating the contralateral lobe of the optic tectum. Between 2 and 40 days later, multiunit activity in response to diffuse light flashes was recorded from the axotomized and normal optic nerves, and from the optic tectum. 2. Two days after tract section, the amplitude of the integrated multiunit response of the axotomized nerve was normal. By 16 days it had fallen to 15% of control values, at which time visual responses carried by the regenerating tract were first recorded in tectum. Activity in the axotomized nerve then recovered gradually. 3. After ablation of one tectal lobe, multiunit responses in the axotomized nerve had not recovered by 40 days. 4. Integrated spontaneous activity in the axotomized nerve was depressed with a similar time course to the depression of light-evoked activity, both after tract section and tectal ablation. 5. Retinal ganglion cell nuclear size, a morphological indicator of the cell body reaction, varied inversely with evoked activity, whether axotomy was by tract section or by tectal ablation. 6. Electrically evoked compound action potentials of normal amplitude could be recorded from an axotomized nerve despite depressed responses to light flashes. 7. It is concluded that optic nerve axotomy in goldfish reduces the number of optic fibres carrying impulses and/or the frequency of their discharge. The effect is closely linked to morphological changes occurring in the retinal ganglion cell bodies. Recovery of impulse activity and morphology depends upon the regenerating optic fibres innervating an appropriate target.
The Journal of Comparative Neurology, 1985
The organization of retinofugal projections was studied in a cichlid fish 'by labelling small groups of retinal ganglion cell axons with either horseradish peroxidase or cobaltous lysine. Two major findings resulted from these (experiments. First, optic tract axons show a greater degree of pathway diversity than was previously appreciated, and this pathway diversity is related to the target nuclei of groups of axons. The most striking example is the formation of the medial optic tract. Fibers that will become the medial optic tract move abruptly away from their neighbors, at about the level of the optic chiasm, and coalesce at the dorsomedial edge of the marginal optic tract. The medial optic tract projects to the thalamus, the dorsal pretectum, and the deep layer of the optic tectum. The axial optic tract is a group of fibers which segregates from 1,he most medial portion of the marginal optic tract, at about the level of the optic chiasm. The axial tract stays medial to the marginal optic tract for a few hundred microns and then curves laterally to rejoin the marginal optic tract. At least some axial trat axons terminate in the suprachiasmatic nucleus. Within the marginal optic tract, retinal ganglion cell axons from a given retinal quadrant are always segregated into at least two groups. The smaller group projects to the superficial pretectal nucleus. The larger group projects to the superficial layer of the optic tectum.
Vision Research, 1991
In normal goldfish, optic axons innervate only the contralateral optic tectum. When one eye was enucleated and the optic nerve of the other eye crushed, the regenerating optic axons innervated both optic tecta. We studied the presence of bilaterally projecting retinal ganglion cells by double retrograde cell labeling methods using Nuclear Yellow and True Blue dyes. About 10% of the retinal ganglion cells were double labeled and these cells were found throughout the retina. In addition, HRP application to the ipsilateral tectum revealed retrogradely-labeled retinal ganglion cells of all morphological types. These results suggest that induced ipsilateral projections are formed by regenerating axon collaterals and that all cell types are involved in the generation of normal mirror image typography.
Anomalous retinal projection after removal of contralateral optic tectum in adult goldfish
Experimental Neurology, 1973
Retinotectal projections were mapped in a series of adult goldfish at various intervals after complete ablation of one tectum, or after enucleation of one eye and removal of its ipsilateral tectum. In the first case, regenerating optic axons entered the ipsilateral tectum and innervated it retinotopically; the normal and ipsilateral projections overlapped each other. In the second case, the remaining eye projected over the remaining ipsilateral tectum in normal retinotopic order. Thus, the presence of already innervated optic tectum does not deter regenerating axons from innervating it. It is suggested that the visual projection of goldfish tends to retain its completeness in the absence of normal terminal spaces.
Experimental Brain Research, 1992
In this study, we crushed one optic nerve in the frog Litoria (Hyla) moorei and at intervals thereafter anterogradely labelled optic axons with horseradish peroxidase (HRP). For one series, HRP was applied between the eye and the crush site and in a second series between the crush site and the chiasm. A tectal projection of regenerating axons was seen in both series but, in addition, up to 12 weeks post-crush, the second series displayed an additional projection. Its appearance matched that of the disconnected, but persisting, optic axon terminals which are found after enucleation or optic nerve ligation. We conclude that, in the frog, many disconnected optic axons persist throughout the period of optic nerve regeneration and of restoration of an orderly retino-tectal map.
Restoration of retino-tectal connections in frogs during regeneration of the optic nerve
Neurophysiology
At various times after unilateral division of the optic nerve in the frogRana temporaria L. evoked potentials in response to electrical stimulation of the optic nerve were investigated in a segment distal to the site of operation, spike activity was recorded from endings of regenerating and intertectal axons when stimuli of different shapes were placed in the field of vision, and the distribution of axonal bulbs of growth by depth in the tectum mesencephal was studied electron-microscopically. During regeneration of the axons the responses of the retinal ganglionic cells to visual stimuli retained most of their individual features. Myelinated axons of the retinal ganglionic cells regenerate first (starting on the 21st day after operation). Myelination of these fibers lags significantly behind their growth and is complete more than 100 days after the operation. Unmyelinated axons of the retinal ganglionic cells grow up toward the tectum mesencephali after myelinated axons (80 or more...
Displaced retinal ganglion cells in normal frogs and those with regenerated optic nerves
Anatomy and Embryology, 1992
We have analysed the number and spatial distribution of displaced retinal ganglion cells in the frog Litoria (Hyla) moorei. A series of normal animals was compared with one in which the optic nerve was crushed and allowed to regenerate. Ganglion cells were labelled with horseradish peroxidase (HRP) applied to the optic nerve, and retinae were examined as sections or whole mounts. We analysed separately ganglion cells with somata displaced to the inner nuclear (Dogiel cells, DGCs) and to the inner plexiform layer (IPLGCs). These findings were related to data for the orthotopic ganglion cells (OGCs). The mean number of DGCs in the normal series was 2,550 (• 281) and fell to 1,630 (_+ 321) after regeneration, representing a mean loss of 36%. This reduction was not significantly different from the mean loss of 43% from the OGC population in which mean values fell from 474,700 (+47,136) to 268,700 (-t-54,395). In both the normal and the regenerate series, DGCs were estimated to represent means of only 0.6% of the OGC population. Densities of DGCs were highest in the nasoventral and temporo-dorsal peripheries; densities of both DGCs and OGCs were lower after optic nerve regeneration. We conclude that the factors which affect ganglion cell death during optic nerve regeneration, do so to similar extents amongst the DGC and the OGC populations. The IPLGCs were very rare in normal animals with a mean of 420 (_+ 95). However, their numbers increased after regeneration to a mean of 3,350 (_+ 690), estimated to be 1.2% of the OGC population. These cells normally favoured peripheral retina but became pan-retinal after regeneration. The primary dendrites of the majority of IPLGCs were oriented in the same direction as those of OGCs. We conclude that most IPLGCs were OGCs which had relocated their somata to the inner plexiform layer.