Displaced retinal ganglion cells project to the accessory optic system in the chameleon ( Chamaeleo calyptratus)

Retinal ganglion cells were successfully labelled in the chameleon by retrograde axonal transport of dextran amines that were applied to the nucleus of the basal optic root (nBOR) in an in vitro preparation. Labelled ganglion cells were restricted to the contralateral eye. Many cells were completely stained including their dendritic trees. With few exceptions, all cells had displaced somata that were located at the inner margin of the inner nuclear layer. The labelled ganglion cells had two to six primary dendrites that branched frequently and formed large unistratified dendritic trees within sublamina 1 of the inner plexiform layer. There was extensive overlap of the dendritic trees of neighbouring cells leading to an estimated coverage factor of 2-4. The dendritic field areas varied in size according to the retinal position of the cells and were highest in the central retina around the fovea with a maximum of 0.14 mm(2) and reached a second maximum at the retinal margin with values of 0.08-0.1 mm(2). The smallest dendritic areas (0.04-0.06 mm(2)) were measured midway between the fovea and retinal margin. The size of the soma area was not correlated to the dendritic field size and increased from 100 to 150 microm(2) near the fovea to 150-300 microm(2) at the retinal margin. There was no evidence for a retinotopic organisation of ganglion cell fibres within the nBOR. All cells were of uniform morphology that was identical to the type of nBOR-projecting displaced ganglion cell (DGC) described previously for the bird retina. Similar to birds, the labelled DGCs were the only source of retinal projection to the nBOR. A small fraction of cells had orthotopic somata located in the ganglion cell layer but were otherwise identical to the labelled DGCs. The similarity of chameleon nBOR-projecting ganglion cells to those described in avian retinas mirrors the close phylogenetic relationship of birds and lizards.     

Is Thy-1 expressed only by ganglion cells and their axons in the retina and optic nerve?

Summary The distribution of Thy-1 in the retina and optic nerve has been examined immunohistochemically, and compared to that of the astrocytic marker glial fibrillary acidic protein. The axons and cell bodies of ganglion cells were found to be Thy-1 positive as were processes within the inner plexiform layer. Transection of the optic nerve in the neonatal rat results in the rapid degeneration of the ganglion cells but some Thy-1 staining remains in the inner plexiform layer. We have estimated using an immunoassay of normal and optic nerve transected retinae that about 70% of the Thy-1 in the retina is on ganglion cells and their axons and the remainder is on cells which contribute processes to the inner plexiform layer, presumably amacrine, bipolar or Müller cells.In the optic nerve the Thy-1 was found to be limited to the fascicles of optic nerve fibres and the intrafascicular spaces, containing astrocytes and their processes, were not stained. Axotomy of the adult nerve, which produced axonal degeneration and astrocytic proliferation, led to a loss of over 95% of the Thy-1 from the nerve. We found no evidence that the astrocytes of the retina or optic nerve were Thy-1 positive in normal animals or during degeneration.     

An immunocytochemical marker for hamster retinal ganglion cells

Summary We examined the specificity and developmental time course of the labelling of retinal ganglion cells in Syrian hamsters by a monoclonal antibody AB5. In adult hamsters, AB5 selectively labelled somata in the ganglion cell layer, dendrites in the inner plexiform layer and axons in the nerve fibre layer. When retinal ganglion cells were retrogradely labelled with Dil prior to AB5 immunocytochemistry, all of the retrogradely labelled retinal ganglion cells in the ganglion cell layer were AB5 immunoreactive, indicating that AB5 labels all classes of ganglion cell in that layer. In retinae depleted of retinal ganglion cells by neonatal optic nerve transections, AB5 did not label any somata or processes, indicating that AB5 specifically labels retinal ganglion cells. During development, AB5 labelling first appeared as a weak staining of cell bodies in the ganglion cell layer on postnatal day 12 (P12; PO=first 24 h following birth) and acquired the staining pattern seen in the adult by postnatal day 14. From the onset of AB5 immunoreactivity, AB5-labelled somata of varying sizes were present across the entire retinal surface. Although AB5 labelled retinal ganglion cell axons in the nerve fibre layer of the retina it did not label the optic nerve or retinal ganglion cell axons in the brain at any age examined. AB5 labelling was also found to be compatible with bromodeoxyuridine immunocytochemistry and, therefore, useful for determining the time of generation of hamster retinal ganglion cells.     

Changes in NADPH diaphorase expression in the fish visual system during optic nerve regeneration and retinal development

The various functions of nitric oxide (NO) in the nervous system are not fully understood, including its role in neuronal regeneration. The goldfish can regenerate its optic nerve after transection, making it a useful model for studying central nervous regeneration in response to injury. Therefore, we have studied the pattern of NO expression in the retina and optic tectum after optic nerve transection, using NADPH diaphorase histochemistry. NO synthesis was transiently up-regulated in the ganglion cell bodies, peaking during the period when retinal axons reach the tectum, between 20–45 days after optic nerve transection. Enzyme activity in the tectum was transiently down-regulated and then returned to control levels at 60 days after optic nerve transection, during synaptic refinement. To compare NO expression in the developing and regenerating retina, we have looked at NO expression in the developing zebrafish retina. In the developing zebrafish retina the pattern of staining roughly followed the pattern of development with the inner plexiform layer and horizontal cells having the strongest pattern of staining. These results suggest that NO may be involved in the survival of ganglion cells in the regenerating retina, and that it plays a different role in the developing retina. In the tectum, NO may be involved in synaptic refinement.     

Neuronal and glial cell types revealed by NADPH-diaphorase histochemistry in the retina of a teleost fish, the grass goby (Zosterisessor ophiocephalus, Perciformes, Gobiidae)

The grass goby is a mud-burrowing fish with a rich retinal vasculature appropriate to its hypoxic habitat. NADPH-diaphorase histochemistry was performed on retinal sections and wholemounts to reveal cells that contain nitric oxide synthase and so may be presumed to synthesise nitric oxide, a gaseous intercellular messenger with many roles including vasodilation. Structures that were consistently stained by this method included cone ellipsoids, horizontal cells, Müller cells and their processes, large displaced ganglion cells in the inner nuclear layer (identified by their axons), large interstitial ganglion cells in the inner plexiform layer, and capillary endothelial cells. In wholemounts, horizontal cells were seen to form a regular pattern, contacting each other at their dendritic terminals. Some cells in the ganglion cell layer were weakly stained, but stained bipolar and amacrine cells were not seen. The diaphorase-positive large ganglion cells all formed large, sparsely branched dendritic trees, arborizing near the scleral border of the inner plexiform layer. The displaced and interstitial cells seemed to belong to distinct morphological types, the interstitial cells having smaller somata and trees. Analysis of their spatial distributions in one representative retina confirmed this: the displaced cells formed a highly regular mosaic with a mean spacing (nearest-neighbour distance) of 303 µm, whereas the interstitial cells formed a separate mosaic, almost as regular but with a smaller mean spacing of 193 µm, rising to 217 µm in a sample that excluded the area retinae temporalis. Spatial correlogram analysis showed that these two mosaics were spatially independent. Nitric oxide probably has many roles in the retina. The presence of its synthetic enzyme in Müller cells, which communicate with retinal blood vessels, is consistent with a role in the control of retinal blood flow. Its function in large, mosaic-forming retinal ganglion cells is unknown.     

Neuronal and glial cell types revealed by NADPH-diaphorase histochemistry in the retina of a teleost fish, the grass goby ( Zosterisessor ophiocephalus , Perciformes, Gobiidae)

The grass goby is a mud-burrowing fish with a rich retinal vasculature appropriate to its hypoxic habitat. NADPH-diaphorase histochemistry was performed on retinal sections and wholemounts to reveal cells that contain nitric oxide synthase and so may be presumed to synthesise nitric oxide, a gaseous intercellular messenger with many roles including vasodilation. Structures that were consistently stained by this method included cone ellipsoids, horizontal cells, Müller cells and their processes, large displaced ganglion cells in the inner nuclear layer (identified by their axons), large interstitial ganglion cells in the inner plexiform layer, and capillary endothelial cells. In wholemounts, horizontal cells were seen to form a regular pattern, contacting each other at their dendritic terminals. Some cells in the ganglion cell layer were weakly stained, but stained bipolar and amacrine cells were not seen. The diaphorase-positive large ganglion cells all formed large, sparsely branched dendritic trees, arborizing near the scleral border of the inner plexiform layer. The displaced and interstitial cells seemed to belong to distinct morphological types, the interstitial cells having smaller somata and trees. Analysis of their spatial distributions in one representative retina confirmed this: the displaced cells formed a highly regular mosaic with a mean spacing (nearest-neighbour distance) of 303 μm, whereas the interstitial cells formed a separate mosaic, almost as regular but with a smaller mean spacing of 193 μm, rising to 217 μm in a sample that excluded the area retinae temporalis. Spatial correlogram analysis showed that these two mosaics were spatially independent. Nitric oxide probably has many roles in the retina. The presence of its synthetic enzyme in Müller cells, which communicate with retinal blood vessels, is consistent with a role in the control of retinal blood flow. Its function in large, mosaic-forming retinal ganglion cells is unknown. Accepted: 29 April 1999     

大鼠视神经切断后视网膜双极细胞PKC-α和recoverin的表达

为了探讨视神经切断后视网膜内部是否存在突触可塑性改变,本实验采用大鼠视神经切断模型,通过免疫组织化学方法检测视神经切断后视网膜双极细胞PKC-α和recoverin的表达变化。结果显示:正常视网膜中,PKC-α和recoverin阳性产物主要见于视网膜内核层、内网层及节细胞层,另外外核层也可见少量recoverin阳性细胞。视神经切断后3d,大鼠视网膜内网层高倍镜下可见PKC-α和recoverin免疫阳性终末的数量开始增加,14d时增至最高,21d、28d呈现逐渐减少的趋势。本研究结果提示视神经切断后视网膜双极细胞与节细胞之间的突触可能存在早期增生,后期溃变的可塑性变化。     

Dendritic morphology and retinal distribution of tyrosine hydroxylase-like immunoreactive amacrine cells in Bufo marinus

Summary Tyrosine hydroxylase-like immunoreactive (TH-IR) amacrine cells (ACs) in the retina of metamorphosing and adult Bufo marinus were visualized, and their retinal distribution established, using immunohistochemistry on retinal wholemount and sectioned material. The somata of TH-IR ACs were located in the innermost part of the inner nuclear layer (INL). Their dendrites branched predominantly in the scieral sublamina of the inner plexiform layer (IPL), with sparse branching also in the vitreal sublamina. In the retinae of metamorphosing animals 592 ± 113 (mean ± S.D.) immunoreactive cells and in adult 5,670 ± 528 cells were found. Usually 1, 2 or 3 stem dendrites arose from the somata of TH-IR cells which branched 2 or 3 times. In the adult retinae the dendritic field sizes of immunoreactive cells were in the range of 0.059 ± 0.012 mm², which resulted in a considerable dendritic overlap across the retina. TH-IR cells were unevenly distributed over the retina, with 72 cells/mm² in the central temporal retina, 45–50 cells/mm² along the naso-temporal axis of the retina and 25 cells/mm² in the dorsal and ventral peripheral retina. The average density was 36 ± 6 cells/mm². A considerable number of TH-IR cells (range 52–133, n=4) were displaced into the ganglion cell layer (GCL) of the retina. The mean soma sizes of immunoreactive cells were significantly higher in the low density (95 ± 13 m²) than in the high cell density areas (86 ± 12 m²). There was also a slight but significant increase of the dendritic field sizes of these cells towards the low cell density areas of the retina. These observations show that the retinal distribution of TH-IR ACs parallels the non-uniform distribution of neurons of the INL demonstrated recently in Bufo marinus (Zhu et al. 1990). The class of TH-IR ACs appears to correspond to a subgroup of morphologically distinct dopaminergic ACs found in a number of other vertebrate species.On leave from Department of Anatomy, Zhanjiang Medical College, Guangdong, People's Republic of China     

Qualitative and quantitative ultrastructural observations on retinal ganglion cell layer of rat after intraorbital optic nerve crush

Summary Rat retinal ganglion cell layer (GCL) was examined ultrastructurally 1–180 days after intraorbital crushing of one optic nerve. It was confirmed quantitatively that axotomized ganglion cells lost cisternal membranes of the rough endoplasmic reticulum (RER) and showed disintegration of Nissl bodies and ribosomal rosettes 3 days postoperatively. Between 60 and 180 days after neurotomy there was partial reversion of the RER towards normal. At postoperative intervals of 14–60 days, chromatin aggregation became conspicuous and some nuclei were prominently furrowed and contained electron-dense inclusions. Concurrently, profiles of dead ganglion cells were encountered. Mean mitochondrial area increased in axotomized neurons but mitochondrial density declined, while the Golgi apparatus, lamellar specializations of the RER and the size of nuclei did not change significantly. Cytoplasmic atrophy was profound, however. Small nerve cells of the GCL appeared morphologically distinct from ganglion cells and did not undergo appreciable alteration.A decline in neuronal density, approximating 35%, occurred between the third and seventh postoperative day and progressed slowly thereafter. Neuronal density was 32% of normal 180 days postoperatively. A temporary increase in glial density 3–28 days after operation was due to microglial hyperplasia. Müller cell and astrocytic processes hypertrophied, infiltrated nerve fibre bundles, and surrounded and intruded into neuronal somata. Bundles of unmyelinated small axons, invested by astrocytes and basal lamina, were present within the necrotic cavity of the lesioned nerve 28–90 days postoperatively and had cytologic features of regenerative axonal sprouts.We conclude that intraorbital optic nerve crush is followed by a noteworthy degree of regenerative axonal sprouting which occurs and persists against a background of slow but relentless decline in the retinal ganglion cell population. This slow decline follows a rapidly-sustained loss of approximately one-third of the axotomized retinal ganglion cells during the first postoperative week. Intraorbital, as opposed to intracranial, injury of the optic nerve appears, paradoxically, to induce both a greater degree of ganglion cell death and a greater amount of regenerative axonal sprouting. Cytologic changes in axotomized retinal ganglion cells resemble those described for other populations of mammalian intrinsic neurons subjected to like injury. However, they differ, especially with regard to patterns of nuclear, nucleolar and RER alteration, from changes observed in peripheral neurons of mammals and intrinsic neurons of submammalian vertebrates that successfully regenerate severed axons. The neuroglial response in the surround of retinal ganglion cells after optic nerve crush is characterized by hypertrophy of astrocytes and Müller cells and a transient, modest increase of microglia. The microglial reaction is clearly less pronounced than that which occurs in the surround of axotomized peripheral neurons of the rat. The data presented here provide qualitative and quantitative cytologic information against which any effects exerted on the axotomy response and optic nerve regeneration by growth-promoting agents may be assessed.     

Survival and axonal regeneration of off-center retinal ganglion cells of adult cats are promoted with an anti-glaucoma drug, nipradilol, but not BDNF and CNTF

OFF-center retinal ganglion cells (RGCs) occupy a smaller proportion than ON RGCs when RGCs regenerate axons into a transplanted peripheral nerve. We examined whether the regeneration ability of OFF RGCs in adult cats was promoted when the numbers of regenerating RGCs were increased with brain-derived neurotrophic factor (BDNF)+ciliary neurotrophic factor (CNTF)+forskolin (BCF) or 3,4-dihydro-8-(2-hydroxy-3-isopropylamino)-propoxy-3-nitroxy-2H-1-benzopyran (nipradilol), an anti-glaucoma drug. ON or OFF RGCs were morphologically determined on the basis of their dendritic ramification in the inner plexiform layer using computational analysis. In the normal intact retina the ratio of ON and OFF RGCs (ON/OFF ratio) was 1.25 (55%/44%); whereas, it was 2.61 in regenerating RGCs with saline injection (control) 6 weeks after peripheral nerve transplantation. Estimated numbers of regenerating ON and OFF RGCs were 2149 and 895, respectively. An injection of BCF increased only numbers of ON RGCs into 5766 (2.7-fold to control) but not that of OFF RGCs, n=858. Nipradilol increased both estimated numbers of ON (11,518, 5.4-fold to control) and OFF RGCs (7330, 8.2-fold to control). In the retinas with optic nerve (OpN) transection and intravitreal saline-, BCF- or nipradilol-injection, numbers of ON and OFF RGCs surviving axotomy showed similar trend to that in regenerating RGCs. Thus, nipradilol promoted the survival and regeneration abilities of both of ON and OFF RGCs whereas BCF only did the abilities of ON RGCs. The distribution of tropo-myosin-related kinase B, BDNF receptor, was sparser in the outer two thirds of inner plexiform layer. The lower surviving ability of OFF-RGCs may be attributed in part to the distribution.     

A specific projection of retinal displaced ganglion cells to the nucleus of the basal optic root in the chicken.

The displaced ganglion cells of Dogiel are a class of retinal ganglion cells whose perikarya are located along the inner margin of the inner nuclear layer. Found in all vertebrate classes, they are particularly conspicuous in avians. Recently, Karten, Fite &; Brecha (1977) found that these cells in the pigeon gave rise to a seemingly exclusive projection to the contralateral nucleus of the basal optic root, the major component of the avian accessory optic system. In the present work, the projections of displaced ganglion cells were investigated in hatchling and adult chickens. The cells were found to project to the nucleus of the basal optic root but not to the tectum. Labeled displaced ganglion cells following injections of horseradish peroxidase into the nucleus of the basal optic root were 15 × 20μm in size in both hatchlings and adults. Labeled cells tended to have a higher concentration in the peripheral than in the central retina. Cells were widely but irregularly spaced, with adjacent cells seldom closer than 100 μm. Up to 7700 displaced ganglion cells were labeled in the adult chicken.These results, together with those of Kartenet al. (1977), suggest that in birds, displaced ganglion cells may constitute a unique class of retinal ganglion cells that project exclusively to the nucleus of the basal optic root. In light of the projections of the nucleus of the basal optic root to the oculomotor complex and vestibulocerebellum, the displaced ganglion cells may be an initial link in a visual pathway involved in the control of oculomotor reflexes.     

Differential effects of axotomy on substance P-containing and nicotinic acetylcholine receptor-containing retinal ganglion cells: time course of degeneration and effects of nerve growth factor.

The time course of degeneration of chick retinal ganglion cells was examined with Nissl stains and immunohistochemical methods for detection of substance P-like immunoreactive and nicotinic acetylcholine receptor immunoreactive neurons. Small lesions were made in the retinae, adjacent to the optic nerve head, and were subsequently sectioned parallel to the vitreal surface, permitting direct comparison of normal and axotomized retinal ganglion cells distal to the site of axon damage. At four and six days after surgery, a large number of degenerating cells with clear cytoplasm and pyknotic nuclei were seen. After eight, 10 and 14 days, many retinal ganglion cells displayed a chromatolytic response with dispersed Nissl granules, eccentric nuclei and the cells appeared crenulated. The number of apparently normal neurons in the ganglion cell layer in the axotomized region was reduced by about 50% six days following surgery, by about 70% on the 10th day and by about 75% on the 17th day. The remaining neurons in the ganglion cell layer were identified as displaced amacrine cells. From day 2 onwards, increased numbers of glial cells were present in the optic fibre, ganglion cell and inner plexiform layers. Many glial cells were enlarged and displayed extensive cytoplasmic processes, while others showed mitotic activity. Somata and proximal dendrites of retinal ganglion cells were intensely stained for substance P-like immunoreactivity at two and four days following surgery. At six, eight and 10 days, staining intensity was markedly reduced though still evident and at 14 and 17 days, substance P-like immunoreactivity had virtually disappeared. The persistence of limited substance P-like immunoreactive ganglion cells 10 days after surgery indicates that these cells have a relatively protracted response to axotomy. Nicotinic acetylcholine receptor-like immunoreactivity in the ganglion cells at two and four days following axotomy was substantially reduced. The majority of faintly stained nicotinic acetylcholine receptor-like immunoreactive ganglion cells, as visualized in counterstained sections, did not exhibit pyknosis in the immediate period following axotomy. Double label studies demonstrated that substance P-like immunoreactive ganglion cells were distinct from the nicotinic acetylcholine receptor-like immunoreactive ganglion cells. In a second set of experiments, nerve growth factor was then placed into the vitreous humor following intra-retinal axotomy. The somata, dendrites and proximal axons of lesioned substance P-like immunoreactive ganglion cells in these retinae were more intensely stained for a longer period of time and appeared more robust than cells from untreated retinae.(ABSTRACT TRUNCATED AT 400 WORDS)     

Myelination of regenerated optic fibers in peripheral nerve graft of adult cats

Retinal ganglion cells of adult cats have the potential to regenerate their axons into autografted peripheral nerve. Two months after transplantation of the sciatic nerve to the axotomized optic stump, regenerated axons were labeled anterogradely with biocytin, and myelin formation by Schwann cells was examined electron microscopically. Both myelinated and unmyelinated fibers were labeled with biocytin. Among 511 axons labeled in three grafts, 96 fibers (18.8%) were myelinated and 415 (81.2%) were unmyelinated. Mean diameter with SD of myelinated fibers was 1.28 ± 0.39 m (range 0.71–2.47) and that of unmyelinated fibers was 0.76± 0.38 m (range 0.18–2.46). The ratio of inner to outer diameters of the myelin sheath (g value) was 0.82, which is close to the value (0.8) for the optic fibers of intact adult cats.     

Somatostatin-like immunoreactive material in associational ganglion cells of human retina

The retinal ganglion cell is classically viewed as the output cell of the retina, sending a single axon via the optic nerve to synapse in visual relay nuclei of the brain. However, some ganglion cells, termed associational ganglion cells, have axons which do not leave the retina and presumably serve intraretinal communication. Using high-affinity and specific monoclonal antibodies to somatostatin-14 and the avidin-biotin-peroxidase immunohistochemical procedure, somatostatin-immunoreactive associational ganglion cells are specifically stained in human retinas obtained at necropsy. These cells are more numerous in the inferior than the superior retina; they have dendrites which ramify in the inner plexiform layer; and they have sparsely branching axons, many of which can be traced over 1 cm. These axons do not enter the optic nerve. They follow remarkably straight courses at the border of the inner plexiform layer and ganglion cell layer and thereby form a gridwork of fibers covering the entire retinal area. These observations verify the existence of associational ganglion cells in the human and establish somatostatin as a neurotransmitter or neuromodulator candidate for these neurons. The morphology of these cells suggests that they are involved in long-distance interactions within the retina.     

A morphometric study of the retinal ganglion cell response to optic nerve severance in the frog Rana pipiens

Summary This study examines the cell body response to axotomy of retinal ganglion cells in the frogRana pipiens. Cell soma sizes were measured in carefully matched regions of Nissl-stained wholemounted retinae after either nerve crush, nerve cut with stump separation, nerve crush with intraocular nerve growth factor (NGF) or nerve cut with NGF applied to the proximal stump. The state of axonal regeneration was also assessed in each case by anterograde transport of HRP.Following nerve crush axons crossed the lesion by 7 days, reached the chiasma by 14 days and entered the tectum around 20–30 days. The normally evenly stained ganglion cells exhibited granular Nissl staining at 7 and 10 days but very little change in soma size. From 10 to 28 days the mean retinal ganglion cell area increased by 102% and maintained this size until at least 75 days. By 102 days soma size had nearly returned to normal. A population of displaced amacrine cells retained a normal appearance and soma size throughout regeneration.Following nerve cut and stump separation the retinal ganglion cells were slightly more reactive in appearance at 7 days after crush but otherwise the soma reaction developed in a similar manner. Axon tracing revealed no extension beyond the lesion site in these animals and therefore the state of axonal growth did not affect the early soma response.NGF applied at the time of the lesion had no detectable effect on the soma reaction.Although many retinal ganglion cells re-establish contact with visual centres after axotomy in the frog, a considerable proportion die. This contrasts with both the goldfish, where all cells regenerate successfully, and various mammals, where none do so and all retinal ganglion cells die. All retinal ganglion cells in the frog undergo reactive changes similar to those of goldfish and there is no sign of the cell shrinkage seen in mammals. Therefore the cell death in frog would appear to be different from that in mammalian retina but similar to that of mammalian peripheral nerve in which chromatolysis generally preceeds death.     

Influence of peripheral nerve grafts on the expression of GAP-43 in regenerating retinal ganglion cells in adult hamsters

Summary We have examined the ability of axotomized retinal ganglion cells in adult hamsters, to regenerate axons into a peripheral nerve graft attached to the optic nerve and the expression of GAP-43 by these neurons. We also examined the effect on these events of transplanting a segment of peripheral nerve to the vitreous body. The left optic nerves in three groups of hamsters were replaced with a long segment of peripheral nerve attached to the proximal stump of the optic nerve 2 mm from the optic disc to induce regeneration of retinal ganglion cells into the peripheral nerve. An additional segment of peripheral nerve was transplanted into the vitreous of the left eye in the second group. The animals from the first and second groups were allowed to survive for 1–8 weeks and the number of regenerating retinal ganglion cells was determined by applying the retrograde tracer, Fluoro-Gold to the peripheral nerve graft and the expression of GAP-43 was studied by immunocytochemistry in the same retinas. As a control, a segment of optic nerve was transplanted into the vitreous body of the left eye in the third group of hamsters. These animals were allowed to survive for 4 weeks and the number of regenerating retinal ganglion cells was counted as in Groups 1 and 2. The percentages of the regenerating retinal ganglion cells which also expressed GAP-43 were very high at all time points in Group 1 (with no intravitreal peripheral nerve) and Group 2 (with intravitreal peripheral nerve) and at 4 weeks for the Group 3 (with intravitreal optic nerve) animals. In addition, the number of regenerating retinal ganglion cells, the number of retinal ganglion cells expressing GAP-43 and the number of regenerating retinal ganglion cells which also expressed GAP-43 were much higher in Group 2 than in Group 1 at all the time points and it was also much higher in Group 2 than in Group 3 at 4 weeks whereas there was no significant difference between the results from Groups 1 and 3 at 4 weeks. These data suggested that there was a close correlation between the number of the axotomized retinal ganglion cells regenerating axons into the peripheral nerve graft attached to the optic nerve and the expression of GAP-43. In addition, the intravitreal peripheral nerve, probably by releasing various neurotrophic factors and by acting synergistically, can enhance the expression of GAP-43 in some of the axotomized retinal ganglion cells and promote the regeneration of retinal ganglion cells into the peripheral nerve graft.     

Retinal ganglion cell death during regeneration of the frog optic nerve is not accompanied by appreciable cell loss from the inner nuclear layer

Summary We estimated cell numbers in the ganglion cell and inner nuclear layers of adult frog (Hyla moorei) retinae, examining normal animals and those with regenerated optic nerves. Analysis of sections stained with cresyl violet showed that cell numbers in a nasotemporal strip, which included the area centralis and visual streak, were comparable between sides for both these cellular layers in normal animals. In line with our previous observations, after optic nerve regeneration cell numbers in the ganglion cell layer had fallen by 35–43% compared to the unoperated sides. By contrast cell numbers remained similar for the inner nuclear layers on the two sides. We conclude that retrograde transneuronal degeneration had not taken place in the inner nuclear layer in response to ganglion cell death.     

Evidence for an amacrine cell system in the ganglion cell layer of the rat retina

In the ganglion cell layer of the rat retina approx 50% of the cells with the Nissl morphology of neurons survive optic nerve section in infant and adult rats and cannot be retrogradely labelled with horseradish peroxidase. The number of neurons which can be retrogradely labelled with horseradish peroxidase from subcortical visual centres is similar to the number of axons in the optic nerve, and it is concluded that the small neurons do not send an axon into the optic nerve. The dendritic tree of the cells which have axons was demonstrated by filling the cells with horseradish peroxidase from the optic nerve. The dendritic structure of the cells which survive optic nerve section was shown by injecting horseradish peroxidase into the retina or impregnating with the Golgi method the cells which survive optic nerve section. A variety of amacrine cells were found in the ganglion cell layer which form branches in the lower part of the inner plexiform layer.It can be concluded that amacrine cells form a substantial number of the neurons in the ganglion cell layer.     

Cell populations of the ganglion cell layer: displaced amacrine and matching amacrine cells in the pigeon retina

Summary The proportion and size distribution of ganglion and non-ganglion cells in the ganglion cell layer of different areas of the pigeon retina was examined in whole-mounts of the retina by retrograde axonal transport of horseradish peroxidase (HRP) from large brain injections. A maximum of 98% of cells were labelled in the red field and a maximum of 77% in the peripheral yellow field. Unlabelled cell bodies were 30% smaller than labelled ganglion cells and had a mean diameter of 6.2 m and a size range of 4 to 9 m. The morphology of cells in the ganglion cell layer was examined by Golgi staining of retinal whole-mounts. Small glia, displaced amacrine and ganglion cells were found. Displaced amacrine cell bodies were about 30% smaller than ganglion cells and their size distribution was similar to the unlabelled cells in HRP preparations. Displaced amacrine cells had small rounded cell bodies (mean diameter 6.2 m) increasing in size with eccentricity, and a unistratified dendritic tree of fine, nearly radial, varicose dendrites in sublamina 4 of the inner plexiform layer. They had elliptical dendritic fields (mean diameter 66 m) aligned parallel to the retina's horizontal meridian. A population of amacrine cells was found with somas at the inner margin of the inner nuclear layer and soma and dendritic morphology matching those of displaced amacrines. These amacrine cells had unistratified dendritic trees at the junction of sublaminae 1 and 2 of the inner plexiform layer. Pigeon displaced amacrine cells and their matching amacrines are similar to starburst cells of the rabbit retina. They may participate in on and off pathways to ganglion cells and their lamination suggests that they are cholinergic.