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PubMed1998

Prenatal development of the vestibular ganglion and vestibulocerebellar fibres in the rat.

We have used carbocyanine dye tracing techniques in conjunction with photoconversion and electronmicroscopy to examine the prenatal development of the central and peripheral processes of those vestibular ganglion cells projecting to the cerebellum. Developmental changes in the number of vestibular ganglion cells were assessed in paraffin-embedded material by nucleolar counting. In agreement with the results of parvalbumin staining, afferents to the cerebellum from the vestibular ganglion pursued a superficial course during early fetal life (E13 to E15). From E16 to E19, this superficial position was progressively lost and vestibulocerebellar fibres were seen to be directed towards the ventricular surface (prospective posterior/inferior vermis). The change in the course of vestibular afferents to the cerebellum coincided with a profound reduction in the number of ganglion cells which could be retrogradely 1a-belled from the cerebellar anlage (mean+/-SD: E16-2040+/-1130; E19-510+/-440). During that same period the total number of vestibular ganglion cells rose to peak at a mean of 9200 at E19, although there was a subsequent decline to an average of 4660 at P0. This population size was maintained through to adult life (4600). We also examined the development of connections between the vestibular ganglion and the vestibular apparatus. Peripheral processes of vestibular ganglion cells invaded the macula utricle and saccule and cristae of the semicircular canals from E13. We found that the peripheral vestibular ganglion cell processes themselves did not show any significant morphological changes from E16 to E21, but the sensory epithelium itself adopts a mature pseudostratified appearance by E21. This suggests that the loss of vestibular ganglion cells from E19 to birth is not related to major morphological changes in the peripheral axons, at least as revealed by carbocyanine dye labelling of these from the cerebellum, but may be associated with differentiation of the sensory epithelium to the mature pseudostratified form. Electronmicroscopy of photoconverted vestibulocerebellar fibres showed that at E14 these afferents were grouped in tight bundles of up to 20 axons. No particular association with the superficially placed external granular layer cells was found at that age. By E16 photoconverted vestibulocerebellar axons were no longer as tightly bundled and could be seen coursing more ventrally through the cerebellar anlage. The findings indicate that vestibulocerebellar fibres are not likely to physically facilitate external granular layer migration, since they do not attain a particularly close structural association with those cells. The observed developmental changes in the number of vestibular ganglion cells projecting to the cerebellum and the total number of vestibular ganglion cells suggests that changes in the course of vestibulocerebellar fibres are associated at first with retraction of cerebellar afferents, and subsequently with developmental cell death in the ganglion.

Afferent Pathways↗
PubMed1986

[Met]- and [Leu]enkephalin-like immunoreactive cell bodies and nerve fibres in the coeliac ganglion of the cat.

The occurrence and distribution of methionine- and leucine-enkephalin-like immunoreactivity were investigated in the cat coeliac ganglion using either the indirect immunoperoxidase method or the peroxidase-antiperoxidase technique. Several antisera raised to methionine- and leucine-enkephalin were used. Their specificity was assessed by incubating sections of the coeliac ganglion with increasing dilutions of antisera and with antisera saturated with their respective antigen. The present study was performed both in untreated and in colchicine-treated cats. Immunoreactive methionine- and leucine-enkephalin-like cell bodies were only visualized in colchicine-treated cats. Two types of labeled cells were observed. The first type had a size similar to that of unlabeled principal ganglion cells. These labeled cells were numerous and scattered throughout the ganglion; they probably represented enkephalin-containing ganglion cells. The second type of immunoreactive cells were of a much smaller size. They were always gathered in small clusters of about 5-15 cells and were not numerous; they presumably represented enkephalin-containing small intensely fluorescent cells. Immunoreactive nerve fibres were mainly observed in untreated cats and accessorily in colchicine-treated cats. In untreated animals dense networks of methionine- and leucine-enkephalin-like immunoreactive fibres were found in the coeliac ganglion. These fibres had numerous varicosities which often closely surrounded unlabeled principal ganglion cells. In colchicine-treated cats some immunoreactive fibres surrounded labeled principal ganglion cell bodies. The present results establish for the first time the presence of enkephalin-like immunoreactive principal ganglion cells in a mammalian sympathetic prevertebral ganglion. The presence of enkephalin-containing principal ganglion cells, small intensely fluorescent cells and nerve terminals, supports an important role of enkephalins in the integrative synaptic activities of cat coeliac ganglion cells.

Animals↗
PubMedDate not supplied

The lipofuscin content of Scarpas ganglion of normal and Menière's disease patients related to age: a histologic and morphometric study.

Vestibular ganglia were removed post mortem from 25 patients with normal inner ear function and 9 patients with known Menière's disease. The lipofuscin content of the ganglion cells of all specimens were analysed and the two groups compared. The age range of the non-Menière's patients was from 14 to 82 years, and of the Menière's patients from 42 to 72 years. All ganglion cells contained lipofuscin, mostly in the form of large granules. Lipofuscin was concentrated in the lateral areas of the ganglion cells and in each polar extension. In both groups the content of lipofuscin in ganglia increased with age. The increase in the Menière cases was greater. In age-matched data no non-Menière's ganglion reached the content of lipofuscin of a Menière's ganglion. The average percentage of lipofuscin in Scarpa's ganglion was determined by counting lipofuscin granule area in different levels of one ganglion. The portion of lipofuscin in the cytoplasm of ganglion cells of the Menière ganglions was increased about 44% compared with the non-Menière ganglions, if the average percentage of lipofuscin was set at 100%. The increase of 44% is nearly constant between 40 and 70 years. This is a relative increase, because the ganglion cells of the Menière's patients are 12% smaller than those of the healthy persons. Taking into account the different sizes of the ganglion cells these is an absolute increase of lipofuscin in the Menière cases of 28%.

Adult↗
PubMed1964

THE GANGLION BLOCKING ACTION OF PROCAINAMIDE.

In cats and rabbits procainamide (20 to 50 mg, intravenously) produced a fall of blood pressure of 20 to 50 mm Hg which reached a maximal effect within 1 min and lasted for about 5 min. Procainamide reduced the pressor responses to nicotine and to carotid arterial occlusion and reduced the depressor response to vagal stimulation, but did not antagonize the actions of adrenaline or noradrenaline on blood vessels. The contractions of the nictitating membrane to stimulation of the preganglionic cervical sympathetic nerve were partially or completely blocked by 20 to 50 mg of procainamide given intravenously. The ganglion blocking effect was more abrupt in onset and more slow to recover than that due to hexamethonium and had about 1/250th of the activity of the latter. Procainamide (1 mg) reduced the acetylcholine output of the perfused superior cervical ganglion to below 30% of the control value and blocked transmission completely. Small doses (10 mug) reduced the acetylcholine output but hardly affected ganglionic transmission. Procainamide, injected into the perfused superior cervical ganglion, blocked contractions elicited by stimulation of the preganglionic cervical sympathetic nerve for a longer period than those produced by acetylcholine injected into the perfusion circuit to the ganglion; the reverse was true for hexamethonium. Procainamide reduced the size of action potentials recorded from the superior cervical ganglion without altering the resting potential of the ganglion. The ganglion blocking activities of procainamide and hexamethonium often potentiated each other, especially when the preparation had been set up for several hours. On the guinea-pig isolated ileum preparation, procainamide (0.5x10(-4) g/ml.) antagonized responses due to acetylcholine, histamine and, most effectively, to nicotine. On the isolated heart, procainamide (1 mg) almost abolished the bradycardia produced by acetylcholine; 10 mg slowed and weakened the heart, while 100 mg stopped it. We conclude that procainamide, like procaine, blocks ganglionic transmission by (1) depressing the release of acetylcholine from preganglionic nerve endings; and (2) competing, with the acetylcholine which is released, for receptor sites on the ganglion cells. The amounts required to produce significant effects in vivo and in vitro are comparable. The methods available for detecting this type of ganglion blocking action are discussed.

Acetylcholine↗
PubMed1983

Developmental relationships between trigeminal ganglia and trigeminal motoneurons in chick embryos. III. Ganglion perikarya direct motor axon growth in the periphery.

The previous study in this series demonstrated that the ingrowth of the central axons of the trigeminal (V) ganglion is prerequisite to V motor axon outgrowth and somatic translocation. In the present experiment we determined whether further interactions with V ganglion cell bodies were required by V motoneurons after the V ganglion innervates the brainstem. Soon after the ganglion axons had penetrated the brainstem they were severed, and a barrier, either permeable or impermeable, was placed between the ganglion cell bodies and the metencephalon. V motor axons grew along aberrant pathways to circumvent the impermeable barriers, many rerouting to reach the V ganglion. Only those V motor nerves which contacted the V ganglion distal to the barrier reached their target musculature in the mandible. The pattern of migration of V motoneurons was normal regardless of the V motor nerve trajectory, but the cell bodies of those axons which did not reach a muscle were not fully differentiated. When permeable barriers (Millipore filters) were implanted, the nerves followed two types of trajectories. If the pore size of the filter was small (0.45 and 0.025 microns), the V motor nerves grew identically to those observed in embryos in which impermeable barriers had been implanted. If the pore size of the filter was large (8.0 and 0.08 microns), the V motor nerve grew along its normal path directly to the barrier. Small axonal bundles from these nerves frequently grew into the filter toward the distal V ganglion. These results indicate that V motor axons preferentially grow to the V ganglion perikarya after exiting from the brainstem. Contact with the V ganglion always results in V motor nerve growth to the mandible while growth of the V motor axons to aberrant target sites only occurs when the axons fail to contact the V ganglion cells distal to the barrier.

Animals↗
PubMed1986

Role of target tissue in regulating the development of retinal ganglion cells in the albino rat: effects of kainate lesions in the superior colliculus.

Kainic acid or ibotenic acid was injected unilaterally into the major target regions of the axons of retinal ganglion cells--the superior colliculus (SC) or dorsal lateral geniculate nucleus (DLG)--of rat pups ranging in age from postnatal day 0 to postnatal day 10 (P0 - P10). While the collicular or geniculate neurons within the injection site died within 48 hours of the injection, damage to axons and terminals of extrinsic origin within the injected region was not apparent. The neuronal degeneration induced by the neurotoxins, observed at both the light and electron microscopic levels, resembled the neuronal degeneration that occurs in the colliculus during normal development. Macrophages were identified in the regions containing degenerating cells. Two to three weeks after the injections of neurotoxin, massive injections of the enzyme, horseradish peroxidase (HRP), were made into the retinorecipient nuclei. After about 24-hour survival time the numbers of retinal ganglion cells were estimated by counting the number of neurons containing HRP reaction products in sample areas distributed in a regular rectangular array across the entire retinal surface. In the animals in which the neurotoxin was injected into the SC during the first 4 postnatal days, there was a substantial reduction (on average 41.5%; the range: 27.5-65.5%) in the normal number (mean value of 113,000--Potts et al.: Dev. Brain Res. 3:481-486, '82) of retinal ganglion cells surviving the period of "naturally occurring ganglion cell death" in the retinae contralateral to the injected SC. By contrast, injections of neurotoxins into the DLG and/or the optic tract of newborn rats did not result in a significant reduction in the numbers of retinal ganglion cells surviving the period of naturally occurring ganglion cell death. The period of sensitivity of retinal ganglion cells to the injection of neurotoxin into the colliculi extends from birth to about the end of the first postnatal week; the greatest sensitivity seems to be restricted to the first 3-4 postnatal days. In the retinae in which the total number (and density) of ganglion cells was substantially reduced by the selective destruction of their target cells, the centro-peripheral difference in the somal diameters of the ganglion cells (apparent in normal animals) was abolished, both amongst the whole population of ganglion cells and amongst the ganglion cells with the largest somata, relatively thick axons, and large-gauge primary dendrites (Class I cells). The number and distribution of the Class I cells in the depleted retinae were, however, unaltered.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1995

Birth dates and survival after axotomy of neurochemically defined subsets of trigeminal ganglion cells.

Trigeminal (V) ganglion cells with different neurochemical phenotypes or different birth dates are affected differently by neonatal axonal transection. The aim of the present study was to determine if V ganglion cell birth date and neurochemical phenotype were correlated and if these two variables could be related to responses to neonatal axonal transection. Immunocytochemistry, histochemistry, and [3H]thymidine labelling were used to determine the birth dates of V ganglion cells recognized by antibodies directed against neurofilament protein (NF), calcitonin gene-related peptide (CGRP), and substance P (SP) and those that bound the lectin Bandierea simplicifolia-I (BS-I). All V ganglion cells were born between embryonic days (E-) 9.5 and 14.5. All ganglion cells were born between E-9.5 and E-14.5. In a normalized population (percentages normalized to equal 100%), over 90% of NF-positive V ganglion cells were born between E-10.5 and E-12.5. The majority of CGRP-positive and SP-positive ganglion cells (> 90%) were generated from E-13.5 to E-14.5 and E-12.5 through E-14.5, respectively. Almost 85% of BS-I-positive ganglion cells were generated on E-12.5 through E-14.5. Previous results and additional data from this study indicated that NF- and BS-I-positive ganglion cells are proportionally more likely to be lost after neonatal axotomy and that SP-positive cells are more likely to remain. The percentage of CGRP-positive cells in the V ganglion was not significantly altered by neonatal infraorbital nerve transection. Overall, these findings do not indicate a strong relationship between cell birth date and the probability of survival after neonatal axonal damage for all V ganglion cell phenotypes.

Animals↗
PubMed2003

Regulation of ganglion cell production by Notch signaling during retinal development.

Although progenitor cells in developing vertebrate retina are capable of producing all retinal cell types, they are competent to produce only certain cell types at a given time, and this competence changes as development progresses. We asked whether a change in progenitor cell competence is primarily responsible for ending production of a specific cell type, the retinal ganglion cell. Reducing Notch expression using an antisense oligonucleotide in vitro or in vivo increased ganglion cell genesis. The antisense treatment could reinitiate ganglion cell genesis after it had terminated in a region of the retina, but only for a brief period. The failure of the Notch antisense treatment to reinitiate ganglion cell production after this period was not due to the lack of receptor or ligand expression, as both Notch-1 and Delta-1 were still expressed. The failure of the Notch antisense treatment to reinitiate ganglion cell production is consistent with the suggestion that the intrinsic competence of progenitor cells changes as development progresses. Because reducing Notch signaling can reinitiate ganglion cell production for a brief period after ganglion cell production has normally ceased, it appears that ganglion cell production initially ends in a region of the retina because of cell-cell interactions and not because progenitor cells lose the competence to make ganglion cells. Notch signaling appears to temporarily prevent production of ganglion cells in a region, while some other signal must initiate a change in progenitor cell competence, thus permanently ending the possibility of further ganglion cell production.

Animals↗
PubMed1986

Distribution and morphology of retinal ganglion cells in the Japanese quail.

A ganglion cell density map was produced from the Nissl-stained retinal whole mount of the Japanese quail. Ganglion cell density diminished nearly concentrically from the central area toward the retinal periphery. The mean soma area of ganglion cells in isodensity zones increased as the cell density decreased. The histograms of soma areas in each zone indicated that a population of small-sized ganglion cells persists into the peripheral retina. The total number of ganglion cells was estimated at about 2.0 million. Electron microscopic examination of the optic nerve revealed thin unmyelinated axons to comprise 69% of the total fiber count (about 2.0 million). Since there was no discrepancy between both the total numbers of neurons in the ganglion cell layer and optic nerve fibers, it is inferred that displaced amacrine cells are few, if any. The spectrum in optic nerve fiber diameter showed a unimodal skewed distribution quite similar to the histogram of soma areas of ganglion cells in the whole retina. This suggests a close correlation between soma areas and axon diameters. Retinal ganglion cells filled from the optic nerve with horseradish peroxidase were classified into 7 types according to such morphological characteristics as size, shape and location of the soma, as well as dendritic arborization pattern. Taking into account areal ranges of somata of each cell type, it can be assumed that most of the ganglion cells in the whole retinal ganglion cell layer are composed of type I, II and III cells, and that the population of uniformly small-sized ganglion cells corresponds to type I cells and is an origin of unmyelinated axons in the optic nerve.

Animals↗
PubMed1988

Functional lamination in the ganglion cell layer of the macaque's retina.

Close to the fovea of the primate retina the ganglion cell layer is at its maximal thickness and several layers of cells deep. In whole-mount preparations in which the ganglion cells had been retrogradely labelled to reveal the dendritic trees we have studied the distribution of the different ganglion cell types across the depth of the ganglion cell layer. The ganglion cells which project to the parvocellular layers (P ganglion cells) are found more vitread than those which project to the magnocellular layers (M ganglion cells). The cells which project to the midbrain lie in the outer part of the ganglion cell layer among the M cells and adjacent to the inner plexiform layer. Within the P and M classes of ganglion cell the On-centre cells lie more vitread than the Off-centre cells. These results are discussed with relation to the proportions of different cell types sampled with intraocular recordings from ganglion cells and the possible significance for the development of different types of ganglion cell.

Animals↗
PubMed1993

Postnatal maturation of human spiral ganglion cells: light and electron microscopic observations.

The presence of two types of ganglion cells, based on cell size and other morphologic parameters, is well established in the adult mammalian and human spiral ganglion. On the other hand, there is little data concerning cell morphology in the neonatal spiral ganglion. The present study was undertaken to evaluate the differences in the morphometry and distribution of cell types in the spiral ganglion of the human neonate as compared to the adult. A total of five human temporal bones from two neonates and three infants were included in this study. Light microscopic analysis of all specimens was performed, and electron microscopic evaluation of a 14 day old neonatal spiral ganglion was accomplished. The segmental density of spiral ganglion cells was higher in the neonate than in the adult. The prevalence of type II spiral ganglion cells was higher in the neonate than has been reported in the adult, particularly in the middle and apical turns where type II cells constituted 24% and 26% of all ganglion cells, respectively. The prevalence of type II ganglion cells decreased with age, particularly in the middle and apical turns. In the neonate, the maximal cross sectional area of type I neurons increased from the base to the apex and seemed to increase with age especially in the basal turn. The present study strongly supports a clear differentiation of type I and type II ganglion cells in the human neonate and that the prevalence of type II cells is greater in the neonate than the adult. This finding is discussed with reference to postnatal development of the spiral ganglion.

Cell Count↗
PubMed1990

Dendritic distribution of two populations of ganglion cells and the retinopetal fibers in the retina of the silver lamprey (Ichthyomyzon unicuspis).

The distribution of ganglion cells in the retina of the silver lamprey, Ichthyomyzon unicuspis, was revealed by retrograde labeling from the optic nerve with horseradish peroxidase (HRP) and fluorescent-labeled dextrans in live animals and with the fluorescent dye DiI in aldehyde-fixed tissue. The majority of ganglion cells (74%) termed the "outer ganglion cells," are multipolar and are located at the vitread boundary of the inner nuclear layer. The remaining ganglion cells (26%), termed the "inner ganglion cells" are bipolar and are distributed in a sublamina within the inner plexiform layer. The dense, dendritic meshwork of the outer ganglion cells is largely restricted to the sclerad half of the inner plexiform layer with some cells possessing dendrites which pass through the inner nuclear layer to terminate within the outer plexiform layer. The dendrites of the inner ganglion cells form a thin, dendritic network apposing the inner limiting membrane. Axons from both populations of ganglion cells originate from dendrites or the soma and form fascicles lying adjacent to the outer ganglion cell somata. Retinopetal fibers, originating from bilaterally distributed neurons of the tegmental midbrain, were thin and varicose and ran parallel to the ganglion cell axons to terminate either with a varicose enlargement or a few short sidebranches in the sclerad third of the inner plexiform layer. The unusual organization of the lamprey retina and outgroup comparison with hagfish suggests that agnathans share a presumably primitive type of retinal ganglion cell organization compared to that of gnathostomes.

Animals↗
PubMedDate not supplied

Morphology, dendritic field size, somal size, density, and coverage of M and P retinal ganglion cells of dichromatic Cebus monkeys.

Male Cebus monkeys are all dichromats, but about two thirds of the females are trichromats. M and P retinal ganglion cells were studied in the male Cebus monkey to investigate the relationship of their morphology to retinal eccentricity. Retinal ganglion cells were retrogradely labeled after optic nerve deposits of biocytin to reveal their entire dendritic tree. Cebus M and P ganglion cell morphology revealed by biocytin retrograde filling is similar to that described for macaque and human M and P ganglion cells obtained by in vitro intracellular injection of HRP and neurobiotin. We measured 264 and 441 M and P ganglion cells, respectively. M ganglion cells have larger dendritic field and cell body size than P ganglion cells at any comparable temporal or nasal eccentricity. Dendritic trees of both M and P ganglion cells are smaller in the nasal than in the temporal region at eccentricities greater than 5 mm and 2 mm for M and P ganglion cells, respectively. The depth of terminal dendrites allows identification of both inner and outer subclasses of M and P ganglion cells. The difference in dendritic tree size between inner and outer cells is small or absent. Comparison between Cebus and Macaca shows that M and P ganglion cells have similar sizes in the central retinal region. The results support the view that M and P pathways are similarly organized in diurnal dichromat and trichromat primates.

Animals↗
PubMedDate not supplied

The number and distribution of bipolar to ganglion cell synapses in the inner plexiform layer of the anuran retina.

The main route of information flow through the vertebrate retina is from the photoreceptors towards the ganglion cells whose axons form the optic nerve. Bipolar cells of the frog have been so far reported to contact mostly amacrine cells and the majority of input to ganglion cells comes from the amacrines. In this study, ganglion cells of frogs from two species (Bufo marinus, Xenopus laevis) were filled retrogradely with horseradish peroxidase. After visualization of the tracer, light-microscopic cross sections showed massive labeling of the somata in the ganglion cell layer as well as their dendrites in the inner plexiform layer. In cross sections, bipolar output and ganglion cell input synapses were counted in the electron microscope. Each synapse was assigned to one of the five equal sublayers (SLs) of the inner plexiform layer. In both species, bipolar cells were most often seen to form their characteristic synaptic dyads with two amacrine cells. In some cases, however, the dyads were directed to one amacrine and one ganglion cell dendrite. This type of synapse was unevenly distributed within the inner plexiform layer with the highest occurrence in SL2 both in Bufo and Xenopus. In addition, SL4 contained also a high number of this type of synapse in Xenopus. In both species, we found no or few bipolar to ganglion cell synapses in the marginal sublayers (SLs 1 and 5). In Xenopus, 22% of the bipolar cell output synapses went onto ganglion cells, whereas in Bufo this was only 10%. We conclude that direct bipolar to ganglion cell information transfer exists also in frogs although its occurrence is not as obvious and regular as in mammals. The characteristic distribution of these synapses, however, suggests that specific type of the bipolar and ganglion cells participate in this process. These contacts may play a role in the formation of simple ganglion cell receptive fields.

Animals↗
PubMed1989

The morphological characterization and distribution of displaced ganglion cells in the anuran retina.

The number, dendritic morphology, and retinal distribution of displaced ganglion cells were studied in two anuran species, Xenopus laevis and Bufo marinus. Horseradish peroxidase or cobaltic lysine complex was applied to the cut end of the optic nerve, and the size, shape, and retinal position of retrogradely filled ganglion cells displaced into the inner nuclear layer were determined in retinal wholemount and sectioned material. Approximately 1% of ganglion cells in Xenopus and 0.1% in Bufo were found to be displaced. In both species, many of the previously described orthotopic ganglion cell types (Straznicky & Straznicky, 1988; Straznicky et al., 1990) were present among displaced ganglion cells. In Xenopus more displaced ganglion cells were found in the retinal periphery than in the retinal center, and they formed 3 or 4 distinct bands around the optic nerve head. In Bufo the incidence of displaced ganglion cells was higher along the visual streak than in the dorsal and ventral peripheral retina. These results indicate that the distribution of displaced ganglion cells approximates the retinal distribution of orthotopic ganglion cells. One of the likely mechanisms to account for this developmental paradox may be that the formation of the inner plexiform layer, adjacent to the ciliary margin, acts as a mechanical barrier by preventing the entry of some of the late developing ganglion cells into the ganglion cell layer.

Animals↗
PubMedDate not supplied

A morphological classification of ganglion cells in the zebrafish retina.

We examined the distribution and morphological types of ganglion cells in the retina of the zebrafish, a model vertebrate genetic organism. Using cresyl violet and methylene blue staining, a prominent central area was observed in the ventral temporal retina. The density of ganglion cell layer neurons averaged from approximately 12,000/mm2 in the dorsal-nasal retina to a peak of approximately 37,000/mm2 in the ventral-temporal retina. Individual zebrafish ganglion cells were labeled by backfilling with DiI through the optic nerve followed by reconstruction using confocal microscopy. The dendritic stratification and branching pattern of each labeled ganglion cell was examined in relation to the borders of the inner plexiform layer (IPL). We identified 11 different morphological types of ganglion cell. The most commonly labeled ganglion cells were two types termed Type III or IV, which displayed highly stratified dendritic arborizations in their respective ON-, OFF-sublaminae of the IPL. Their dendritic branching patterns were highly asymmetric with many thorn-like varicosities that profusely filled the area of arborization. In contrast, Type V cells formed a small simply branching dendritic field in the innermost portion of the ON-sublamina of the IPL. Two large ganglion cell types (Types I and II) with wide monostratified dendritic fields were found in both the ON- and OFF-sublamina of the IPL. Three different types of multistratified/bistratified ganglion cells were found (Types, IX, X, and XI.) whose dendrites occupied different regions of the IPL. The multistratified dendrites of IX cells occupied the whole width of the IPL, while the dendrites of Type XI cells formed vertical claw-like endings in only the ON-sublamina of the IPL. We conclude that zebrafish ganglion cells display a rich variety of types and branching patterns. This study establishes a series of baseline measurements of zebrafish ganglion cells to facilitate examination of genes playing a role in the specification and stratification of ganglion cell types.

Animals↗
PubMedDate not supplied

Melanopsin and non-melanopsin expressing retinal ganglion cells innervate the hypothalamic suprachiasmatic nucleus.

Retinal input to the hypothalamic suprachiasmatic nucleus (SCN) synchronizes the SCN circadian oscillator to the external day/night cycle. Retinal ganglion cells that innervate the SCN via the retinohypothalamic tract are intrinsically light sensitive and express melanopsin. In this study, we provide data indicating that not all SCN-projecting retinal ganglion cells express melanopsin. To determine the proportion of ganglion cells afferent to the SCN that express melanopsin, ganglion cells were labeled following transsynaptic retrograde transport of a recombinant of the Bartha strain of pseudorabies virus (PRV152) constructed to express the enhanced green fluorescent protein (EGFP). PRV152 injected into the anterior chamber of the eye retrogradely infects four retinorecipient nuclei in the brain via autonomic circuits to the eye, resulting in transneuronally labeled ganglion cells in the contralateral retina 96 h after intraocular infection. In animals with large bilateral lesions of the lateral geniculate body/optic tract, ganglion cells labeled with PRV152 are retrogradely infected from only the SCN. In these animals, most PRV152-infected ganglion cells were immunoreactive for melanopsin. However, a significant percentage (10-20%) of EGFP-labeled ganglion cells did not express melanopsin. These data suggest that in addition to the intrinsically light-sensitive melanopsin-expressing ganglion cells, conventional ganglion cells also innervate the SCN. Thus, it appears that the rod/cone system of photoreceptors may provide signals to the SCN circadian system independent of intrinsically light-sensitive melanopsin ganglion cells.

Animals↗
PubMedDate not supplied

The number, morphology, and distribution of retinal ganglion cells and optic axons in the Australian lungfish Neoceratodus forsteri (Krefft 1870).

Australian lungfish Neoceratodus forsteri may be the closest living relative to the first tetrapods and yet little is known about their retinal ganglion cells. This study reveals that lungfish possess a heterogeneous population of ganglion cells distributed in a horizontal streak across the retinal meridian, which is formed early in development and maintained through to adult stages. The number and complement of both ganglion cells and a population of putative amacrine cells within the ganglion cell layer are examined using retrograde labelling from the optic nerve and transmission electron-microscopic analysis of axons within the optic nerve. At least four types of retinal ganglion cells are present and lie predominantly within a thin ganglion cell layer, although two subpopulations are identified, one within the inner plexiform and the other within the inner nuclear layer. A subpopulation of retinal ganglion cells comprising up to 7% of the total population are significantly larger (>400 microm2) and are characterized as giant or alpha-like cells. Up to 44% of cells within the retinal ganglion cell layer represent a population of presumed amacrine cells. The optic nerve is heavily fasciculated and the proportion of myelinated axons increases with body length from 17% in subadults to 74% in adults. Spatial resolving power, based on ganglion cell spacing, is low (1.6-1.9 cycles deg(-1), n = 2) and does not significantly increase with growth. This represents the first detailed study of retinal ganglion cells in sarcopterygian fish, and reveals that, despite variation amongst animal groups, trends in ganglion cell density distribution and characteristics of cell types were defined early in vertebrate evolution.

Amacrine Cells↗