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PubMedDate not supplied

Development of dendritic trees of rabbit retinal alpha ganglion cells: relation to differential retinal growth.

To provide a quantitative description of the postnatal development of dendritic trees in alpha ganglion cells of the rabbit retina, these cells were stained either by intracellular injection of Lucifer yellow or by application of the lipophilic dye DiI. This was done at three developmental stages: postnatal day (P) 8/9, P 16/17, and in adults. For different retinal locations we quantified the alpha cell dendritic field area, the number of dendritic branch points, and the average dendritic length between branch points. According to the alpha cell location, the data were collected in three groups representing the retinal center, midperiphery, and far periphery, respectively. The data were then correlated with the postnatal retinal expansion which is known to differ among the above topographic regions of the retinae (Reichenbach et al., 1993). Our results show that the growth of alpha ganglion cell dendrites is not proportional to, but significantly exceeds, that of the local retinal tissue. Between P 8/9 and adulthood, the area of central alpha cells increases almost six-fold from 26,000 to 144,000 microns 2 (retinal expansion: 2.2-fold), and that of peripheral cells more than 15-fold from 35,000 to 556,000 microns 2 (retinal expansion: four-fold). During this period, the coverage factor of alpha cell dendritic fields increases about three-fold, and reaches adult levels of about 3 (retinal center) and 2.2 (periphery), respectively. The number of dendritic branch points remains nearly constant, and the distance between them increases by a factor close to the square root of the factor by which the dendritic field area grows. Thus, it appears that, from the second postnatal week on, dendritic trees of rabbit alpha ganglion cells increase by intense "interstitial growth," rather than by outgrowth of (new) dendritic branches. This growth pattern is different from that of some other rabbit retinal ganglion cell types, and of alpha ganglion cells of the cat retina, whose dendritic trees expand at a rate equal to or less than that of the surrounding retinal tissue. The consequences for synaptic contacts with bipolar and amacrine cells are discussed; they suggest a high degree of synaptic plasticity during normal postnatal retinal growth.

Animals↗
PubMedDate not supplied

Extra-receptive-field motion facilitation in on-off directionally selective ganglion cells of the rabbit retina.

The excitatory receptive-field centers of On-Off directionally selective (DS) ganglion cells of the rabbit retina correspond closely to the lateral extent of their dendritic arborizations. Some investigators have hypothesized from this that theories for directional selectivity that entail a lateral spread of excitation from outside the ganglion cell dendritic tree, such as from starburst amacrine cells, are therefore untenable. We show here that significant motion facilitation is conducted from well outside the classical excitatory receptive-field center (and, therefore, dendritic arborization) of On-Off DS ganglion cells for preferred-direction, but not null-direction moving stimuli. These results are consistent with a role in directional selectivity for cells with processes lying beyond the On-Off ganglion cell's excitatory receptive-field center. These results also highlight the fundamental distinction in retinal ganglion cell receptive-field organization between classical excitatory mechanisms and those that facilitate other excitation without producing directly observable excitation by themselves.

Animals↗
PubMedDate not supplied

Topography of ganglion cells and photoreceptors in the retina of a New World monkey: the marmoset Callithrix jacchus.

We studied the anatomical substrates of spatial vision in a New World monkey, the marmoset Callithrix jacchus. This species has good visual acuity and a foveal specialization which is qualitatively similar to that of humans and other Old World primates. We measured the spatial density of retinal ganglion cells and photoreceptors, and calculated the relative numbers of these cell populations. We find that ganglion cells outnumber photoreceptors by between 2.4:1 and 4.2:1 in the fovea. The peak sampling density of ganglion cells is close to 550,000 cells/mm2. This value falls by almost 1000-fold between the fovea and peripheral retina; a value which approaches recent estimates of the centroperipheral ganglion cell gradient for human and macaque monkey retina and primary visual cortex. The marmoset shows a sex-linked polymorphism of color vision: all male and some female marmosets are dichromats. Six of the retinas used in the present study came from animals whose chromatic phenotype was identified in electrophysiological experiments and confirmed by polymerase chain reaction (PCR) amplification of cone opsin encoding genes. One animal was a trichromat and the others were dichromats. Antibodies against short wavelength-sensitive (SWS) cones labeled close to 8% of all cones near the fovea of one dichromat animal, consistent with electrophysiological evidence that the SWS system is present in all marmosets. The topography and spatial density of cone photoreceptors and ganglion cells was similar to that reported for macaque retina, and we found no obvious difference between dichromatic and trichromatic marmoset retinas. These results reinforce the view that the main determinate of primate foveal topography is the requirement for maximal spatial resolution.

Animals↗
PubMedDate not supplied

Biplexiform ganglion cells, characterized by dendrites in both outer and inner plexiform layers, are regular, mosaic-forming elements of teleost fish retinae.

Biplexiform ganglion cells were labelled by retrograde transport of HRP in five species of marine fish from the neoteleost acanthopterygian orders Perciformes and Scorpaeniformes. Their forms and spatial distributions were studied in retinal flatmounts and thick sections. Biplexiform ganglion cells possessed sparsely branched, often varicose, dendrites that ramified through the inner nuclear layer (INL) to reach the outer plexiform layer (OPL), as well as conventional arborizations in the most sclerad part of the inner plexiform layer (IPL). Their somata were of above-average size and were displaced into the vitread border of the INL. Mean soma areas ranged from 99 +/- 6 microns2 in Bathymaster derjugini (Perciformes) to 241 +/- 12 microns2 in Hexagrammos stelleri (Scorpaeniformes), but were similar in each species to those of the outer-stratified alpha-like ganglion cells, whose dendritic trees occupied the same IPL sublamina. In the best-labelled specimens, biplexiform cells formed clear mosaics with spacings and degrees of regularity much like those of other large ganglion cells, but spatially independent of them. Biplexiform mosaics were plotted in three species, and analyzed by nearest-neighbor distance and spatial correlogram methods. The exclusion radius, an estimate of minimum mosaic spacing, ranged from 113 microns in Hexagrammos stelleri, through 150 microns in Ernogrammus hexagrammus (Perciformes), to 240 microns in Myoxocephalus stelleri (Scorpaeniformes). A spatial cross-correlogram analysis of the distributions of biplexiform and outer-stratified alpha-like cells in Hexagrammos demonstrated the spatial independence of their mosaics. Similar cells were previously observed not only in the freshwater cichlid Oreochromis spilurus (Perciformes) but also in the goldfish Carassius auratus (Cypriniformes) which, being an ostariophysan teleost, is only distantly related. Thus, biplexiform ganglion cells may be regular elements of all teleost fish retinae. Their functional role remains unknown.

Animals↗
PubMedDate not supplied

Potassium-evoked directionally selective responses from rabbit retinal ganglion cells.

Previous studies have shown that directionally selective (DS) retinal ganglion cells cannot only discriminate the direction of a moving object but they can also discriminate the sequence of two flashes of light at neighboring locations in the visual field: that is, the cells elicit a DS response to both real and apparent motion. This study examines whether a DS response can be elicited in DS ganglion cells by simply stimulating two neighboring areas of the retina with high external K+. Extracellular recordings were made from ON-OFF DS ganglion cells in superfused rabbit retinas, and the responses of these cells to focal applications of 100 mM KCl to the vitreal surface of the retina were measured. All cells produced a burst of spikes (typically lasting 50-200 ms) when a short pulse (10-50 ms duration) of KCl was ejected from the tip of a micropipette that was placed within the cell's receptive field. When KCl was ejected successively from the tips of two micropipettes that were aligned along the preferred-null axis of a cell, sequence-dependent responses were observed. The response to the second micropipette was suppressed when mimicking motion in the cell's null direction, whereas an enhancement during apparent motion in the opposite direction frequently occurred. Sequence discrimination in these cells was eliminated by the GABA antagonist picrotoxin and by the Ca(2+)-channel blocker omega-conotoxin MVIIC, two drugs that are known to abolish directional selectivity in these ganglion cells. The spatiotemporal properties of the K(+)-evoked sequence-dependent responses are described and compared with previous findings on apparent motion responses of ON-OFF DS ganglion cells.

Animals↗
PubMedDate not supplied

Soma and axon diameter distributions and central projections of ferret retinal ganglion cells.

Using a combination of retrograde horseradish peroxidase (HRP) labelling, silver staining, and electron microscopy, we have assessed the relationship between retinal ganglion cell soma size and axon diameter in the adult ferret (Mustela putorius furo). Retinal ganglion cells were labelled following injections of HRP into the lateral geniculate nucleus (LGN), superior colliculus (SC), or LGN+SC. The soma size distributions following LGN, SC, or LGN+SC injections were all unimodal showing considerable overlap between different cell classes. This was confirmed for alpha cells identified on the basis of dendritic filling or from neurofibrillar-stained retinae. Analysis of the soma size and axon diameters of a population of heavily labelled retinal ganglion cells showed a significant correlation between the two. However, the overall distribution of intraretinal axon diameter was bimodal with an extended tail. Analysis of the ganglion cell distributions in the adult ferret indicates that beta cells comprise about 50.5-55%, gamma 42.5-47%, and alpha 2.5% of the ganglion cell population. This implies that the proportion of gamma, beta, alpha cells in both cat and ferret retina is highly conserved despite differences in visual specialization in the two species.

Animals↗
PubMedDate not supplied

Retinotopic organization of the superior colliculus in relation to the retinal distribution of afferent ganglion cells.

Sensory representations in the brain exhibit topographic variations in magnification. These variations have been thought to reflect regional differences in the density of innervation at the sensory receptor surface. In the primate visual cortex, for example, local magnification factors have been reported to be proportional to the corresponding densities of retinal ganglion cells. We sought to learn whether this principle also operates in a second major retinofugal pathway--the projection to the superior colliculus. In cats, we first used retrograde transport to determine the retinal distributions of the ganglion cells that project to the colliculus. Then, we compared the numbers of colliculopetal ganglion cells in selected retinal sectors to the areas of the corresponding collicular representations. Collicular areal magnification was not simply proportional to the density of afferent ganglion cells, being instead at least 5-fold greater than expected in the representation of the central visual field. These data imply that incoming retinal afferents are more widely spaced in the central regions of the tectal map than in the map's periphery. Such variations in afferent density appear to play as large a role as the distribution of ganglion cells in determining the metric of the collicular map.

Afferent Pathways↗
PubMed1992

A slowly inactivating K+ current in retinal ganglion cells from postnatal rat.

The whole-cell configuration of the patch-clamp technique was used to study voltage-gated K+ conductances in retinal ganglion cells from postnatal rat. Retinal ganglion cells were fluorescently labeled in situ, dissociated from the retina, and maintained in culture. With physiological solutions in the bath and the pipette, depolarizing voltage steps from physiological holding potentials activated Na(+)-(INa), Ca2+ (ICa), and K(+)-currents studied previously in retinal ganglion cells. Here we report on a slowly decaying K+ current, not heretofore reported in rat. With 4-AP, TEA, and Co2+ in the bath, to block IA, IK, and IK(Ca), respectively, a slowly decaying outward current was activated from -80 mV by steps positive to -40 mV. This current was present in 92% of all ganglion cells tested (n = 83). It activated within 10 ms and inactivated with a voltage-independent time constant of about 70 ms at 35 degrees C. Inactivation was voltage-dependent, half-maximal at -55 mV, and almost complete at 0 mV. The current was blocked by internal Cs+ and TEA, or by external application of 1 mM Ba2+, but not by 3 mM extracellular Co2+. The biophysical and pharmacological properties of this current are distinctly different from those of slowly inactivating K+ currents studied in other rat neurons. It was very similar, however, to a slowly inactivating K+ current previously reported in ganglion cells of tiger salamander retina. This last finding indicates conservation of a defined K+ channel type in functionally related cells in both lower vertebrates and mammals.

4-Aminopyridine↗
PubMedDate not supplied

The neurotensin-related hexapeptide LANT6 is found in retinal ganglion cells and in their central projections in pigeons.

Previous biochemical and immunohistochemical studies have shown that the neurotensin-related hexapeptide LANT6 is widespread and abundant in the avian nervous system. In the present study, immunohistochemical techniques were used to show that LANT6 is present in numerous cells of the retinal ganglion cell layer in pigeons. Consistent with the possibility that these LANT6+ retinal cells might be retinal ganglion cells, it was found that (1) the distribution of LANT6+ fibers and terminals in the central retinal target areas matched the distribution of central retinal projections; (2) the LANT6+ fibers and terminals are eliminated from retinal target areas by transection of the contralateral optic nerve; and (3) LANT6+ retinal cells in the ganglion cell layer can be retrogradely labeled by injections of fluorogold in the tectum. These results suggest that LANT6 may be utilized as a neuroactive substance by the central terminals of numerous retinal ganglion cells in birds. Similar anatomical findings have been previously reported for members of several other vertebrate groups, giving rise to the possibility that LANT6 (or its homologues in nonavians) may be a phylogenetically ubiquitous neuroactive substance used by retinal ganglion cells.

Animals↗
PubMedDate not supplied

Estimating the contributions of NMDA and non-NMDA currents to EPSPs in retinal ganglion cells.

Whole-cell recordings were obtained from retinal ganglion cells of the tiger salamander (Ambystoma tigrinum) in a superfused slice preparation to evaluate contributions of NMDA (N-methyl-D-aspartate) and KA/AMPA (kainate/alpha-amino-3-hydroxy-5-methyl-4-isoxalone propionic acid) receptors to excitatory postsynaptic potentials (EPSPs) of retinal ganglion cells. Synaptic activation of retinal ganglion cells was achieved through the use of a brief pressure pulse of hyperosmotic Ringer (Ringer + sucrose) delivered through a microelectrode visually placed in the inner plexiform layer while whole-cell recordings were obtained from adjacent cells in the ganglion cell layer. Separation of NMDA and KA/AMPA excitatory postsynaptic currents (EPSCs) was achieved through the application of the antagonists NBQX and D-AP7, while inhibitory currents were blocked by strychnine and picrotoxin. Simple addition of the two independent EPSCs showed, most often, that the sum of the KA/AMPA and NMDA currents was less than the control response, but in some cases the sum of the two currents exceeded the magnitude of the control response. Neither result was consistent with expectations based on voltage-clamp principles and the assumption that the two currents were independent; for this reason, we considered the possibility of nonlinear interactions between KA/AMPA and NMDA receptors. Computer simulations were carried out to evaluate the summation experiments. We used both an equivalent cylinder model and a more realistic, compartmental model of a ganglion cell constrained by a passive leakage conductance, a linear KA/AMPA synaptic current, and a nonlinear NMDA current based on the well-known, voltage-sensitive Mg2+ block. Computer simulation studies suggest that the hypo- and hyper-summation of NMDA and KA/AMPA currents, observed physiologically, can be accounted for by a failure to adequately space clamp the neuron. Clamp failure leads to enhanced NMDA currents as the ion channels are relieved of the Mg2+ block; their contribution is thus exaggerated depending on the magnitude of the conductance change and the spatial location of the synaptic input.

2-Amino-5-phosphonovalerate↗
PubMedDate not supplied

Large retinal ganglion cells that form independent, regular mosaics in the ranid frogs Rana esculenta and Rana pipiens.

Population-based studies of ganglion cells in retinal flatmounts have helped to reveal some of their natural types in mammals, teleost fish and, recently, the aquatic mesobatrachian frog Xenopus laevis. Here, ganglion cells of the semiterrestrial neobatrachian frogs Rana esculenta and Rana pipiens have been studied similarly. Ganglion cells with large somata and thick dendrites could again be divided into three mosaic-forming types with distinctive stratification patterns. Cell dimensions correlated inversely with density, being smallest in the visual streak. Cells of the alpha a mosaic (< 0.2% of all ganglion cells) had the largest somata at each location (often displaced) and their trees were confined to one shallow plane within sublamina a of the inner plexiform layer. In regions of high regularity, many trees were symmetric. Elsewhere, asymmetric, irregular trees predominated and their dendrites, although sparsely branched, achieved consistent coverage by intersecting in complex ways. Cells of the alpha ab mosaic were more numerous (approximately 0.7%) and had large somata, smaller (but still large) trees, and dendrites that branched extensively in two separate shallow planes in sublaminae a and b. The subtrees did not always match in symmetry, and each subtree tessellated independently with its neighbors. Cells of the alpha c mosaic (approximately 0.1%) had large, orthotopic somata and large, sparse trees (often asymmetric and irregular) close to the ganglion cell layer. Nearest-neighbor analyses and spatial correlograms confirmed that each mosaic was regular and independent. Densities, proportions, sizes, and mosaic statistics are tabulated for all three types, which are compared with types defined by size and symmetry in R. pipiens, by discriminant analysis in R. temporaria, by physiological response in both, and by mosaic analysis in Xenopus and several teleosts. The variable stratification of these otherwise similar types across species is consistent with other evidence that stratification may be determined, in part, by functional interactions.

Animals↗
PubMedDate not supplied

Dendritic development of retinal ganglion cells after prenatal intracranial infusion of tetrodotoxin.

The dendritic form of a cell may be established by many factors both intrinsic and environmental. Blockade of action potentials along the course of axons and in their postsynaptic targets dramatically alters the development of axonal morphology. The extent to which blockade of target cell activity retrogradely alters the dendritic morphology of the presynaptic cells is unknown. To determine whether the establishment of dendritic form by developing retinal ganglion cells depends on activity within their targets, the sodium channel blocker, tetrodotoxin (TTX), was administered via minipumps to the diencephalon of cat fetuses from embryonic day 43 (E43) to E57. At E57 retinae were removed and living retinal ganglion cells injected in vitro with Lucifer yellow to reveal their dendritic morphology. In the TTX-treated animals both alpha and beta types of retinal ganglion cells were present, as were putative gamma cells. Overall, the dendrites of retinal ganglion cells in TTX-treated animals appeared qualitatively and quantitatively similar to those of untreated animals. The only significant change in the TTX-treated cases was a small increase in the number of dendritic spines on the non-beta cells. These results indicate that the acquisition of basic dendritic form of developing ganglion cells is not influenced by the action potential activity within their targets, and that it is also independent of the terminal branching patterns of their axons.

Action Potentials↗
PubMedDate not supplied

Morphology of wide-field bistratified and diffuse human retinal ganglion cells.

To study the detailed morphology of human retinal ganglion cells, we used intracellular injection of horseradish peroxidase and Neurobiotin to label over 1,000 cells in an in vitro, wholemount preparation of the human retina. This study reports on the morphology of 119 wide-field bistratified and 42 diffuse ganglion cells. Cells were analyzed quantitatively on the basis of dendritic-field size, soma size, and the extent of dendritic branching. Bistratified cells were similar in dendritic-field diameter (mean +/- S.D. = 682 +/- 130 microm) and soma diameter (mean +/- S.D. = 18 +/- 3.3 microm) but showed a broad distribution in the extent of dendritic branching (mean +/- S.D. branch point number = 67 +/- 32; range = 15-167). Differences in the extent of branching and in dendritic morphology and the pattern of branching suggest that the human retina may contain at least three types of wide-field bistratified cells. Diffuse ganglion cells comprised a largely homogeneous group whose dendrites ramified throughout the inner plexiform layer. The diffuse cells had similar dendritic-field diameters (mean +/- S.D. = 486 +/- 113 microm), soma diameters (mean +/- S.D. = 16 +/- 2.3 microm), and branch points numbers (mean +/- s.D. = 92 +/- 32). The majority had densely branched dendritic trees and thin, very spiny dendrites with many short, fine, twig-like thorny processes. Five of the diffuse cells had much more sparsely branched dendritic trees (<50 branch points) and less spiny dendrites, suggesting that there are possibly two types of diffuse ganglion cells in human retina. Although the presence of a diversity of large bistratified and diffuse ganglion cells has been observed in a variety of mammalian retinas, little is known about the number of cell types, their physiological properties, or their central projections. Some of the human wide-field bistratified cells in the present study, however, show morphological similarities to monkey large bistratified cells that are known to project to the superior colliculus.

Adolescent↗
PubMedDate not supplied

Expression and distribution of ionotropic glutamate receptor subunits on parasol ganglion cells in the primate retina.

The response properties of postreceptoral sensory neurones are determined by the properties of their input neurones, by intrinsic membrane properties, and by the properties of neurotransmitter receptors on the soma and dendritic tree. We previously showed that inhibitory neurotransmitter (GABA(A) and glycine) receptors on a well-characterised sensory neurone, the parasol ganglion cell in the primate retina, are segregated towards the distal part of the dendritic tree. Here we studied the distribution of excitatory ionotropic glutamate receptor subunits on the dendrites of parasol cells in the retina of a New World monkey, the marmoset, Callithrix jacchus. Individual ganglion cells were intracellularly injected in an in vitro retinal wholemount preparation. Ionotropic glutamate receptor subunits. including AMPA (GluR1-4), kainate (GluR6/7), NMDA (NR1C2') subunits, and the orphan receptors delta1 and delta2 were visualized with immunocytochemical methods. Immunoreactive puncta that colocalized with the dendrites of ganglion cells were analyzed using standard and/or confocal light microscopy. Colocalized puncta were present on parasol dendrites for all subunits studied, but their density was much lower (approximately 1/5) than previously reported for inhibitory (GABA and glycine) receptors. Segregation of the glutamate receptor clusters (GluR1, GluR6/7 subunits) to the peripheral dendrites was less marked than that shown for GABA and glycine receptor clusters. No sign of segregation of colocalized puncta to the peripheral part of the dendritic field was seen with antibodies to the GluR2, GluR2/3, GluR4, delta1/2, or NR1C2' subunits. The results suggest that although there is diverse expression of glutamate receptor subtypes, the glutamatergic synapses form only a small proportion of the total synaptic input to primate ganglion cells. They further suggest that the processes which control distribution of excitatory and inhibitory synapses on the dendritic field of ganglion cells are, at least to some extent, independent.

Animals↗
PubMedDate not supplied

Mosaic properties of midget and parasol ganglion cells in the marmoset retina.

We measured mosaic properties of midget and parasol ganglion cells in the retina of a New World monkey, the common marmoset Callithrix jacchus . We addressed the functional specialization of these populations for color and spatial vision, by comparing the mosaic of ganglion cells in dichromatic ("red-green color blind") and trichromatic marmosets. Ganglion cells were labelled by photolytic amplification of retrograde marker ("photofilling") following injections into the lateral geniculate nucleus, or by intracellular injection in an in vitro retinal preparation. The dendritic-field size, shape, and overlap of neighboring cells were measured. We show that in marmosets, both midget and parasol cells exhibit a radial bias, so that the long axis of the dendritic field points towards the fovea. The radial bias is similar for parasol cells and midget cells, despite the fact that midget cell dendritic fields are more elongated than are those of parasol cells. The dendritic fields of midget ganglion cells from the same (ON or OFF) response-type array show very little overlap, consistent with the low coverage of the midget mosaic in humans. No large differences in radial bias, or overlap, were seen on comparing retinae from dichromatic and trichromatic animals. These data suggest that radial bias in ganglion cell populations is a consistent feature of the primate retina. Furthermore, they suggest that the mosaic properties of the midget cell population are associated with high spatial resolution rather than being specifically associated with trichromatic color vision.

Animals↗
PubMedDate not supplied

Ganglion cells of a short-wavelength-sensitive cone pathway in New World monkeys: morphology and physiology.

We have studied the morphology and physiology of retinal ganglion cells of a short-wavelength-sensitive cone (SWS-cone) pathway in dichromatic and trichromatic New World anthropoids, the capuchin monkey (Cebus apella) and tufted-ear marmoset (Callithrix jacchus). In Old World anthropoids, in which males and females are both trichromats, blue-ON/yellow-OFF retinal ganglion cells have excitatory SWS-cone and inhibitory middle- and long-wavelength-sensitive (MWS- and LWS-) cone inputs, and have been anatomically identified as small-field bistratified ganglion cells (SB-cells) (Dacey & Lee, 1994). Among retinal ganglion cells of New World monkeys, we find SB-cells which have very similar morphology to such cells in macaque and human; for example, the inner dendritic tree is larger and denser than the outer dendritic tree. We also find blue-on retinal ganglion cells of the capuchin to have physiological responses strongly resembling such cells of the macaque monkey retina; for example, responses were more sustained, with a gentler low frequency roll-off than MC-cells, and no evidence of contrast gain control. There was no difference between dichromatic and trichromatic individuals. The results support the view that SWS-cone pathways are similarly organized in New and Old World primates, consistent with the hypothesis that these pathways form a phylogenetically ancient color system.

Animals↗
PubMedDate not supplied

Midget and parasol ganglion cells of the primate retina express the alpha1 subunit of the glycine receptor.

Glycine is a major inhibitory neurotransmitter in the mammalian retina and has been shown to influence the responses of ganglion cells. Midget and parasol ganglion cells serve distinct physiological roles in the primate retina and show differences in their response characteristics to light stimuli. In the present study, we addressed the question of whether the expression of glycine receptors differs in midget and parasol ganglion cells. Ganglion cells in the retinae of marmoset and macaque monkeys were injected with Neurobiotin in a live in vitro retinal whole-mount preparation. Retinal pieces were then processed with an antibody against the alpha1 subunit of the glycine receptor. Strong punctate immunoreactivity indicative of synaptic localization is present in the ON and OFF sublamina of the inner plexiform layer. Many of the immunoreactive puncta coincide with the dendrites of both midget and parasol ganglion cells. Immunoreactive puncta are present on distal and proximal dendrites of ON and OFF cells. These results suggest that ON and OFF midget and parasol cells do not differ with respect to the distribution of the alpha1 subunit of the glycine receptor.

Animals↗
PubMed1997

Combined retrograde tracing and immunohistochemistry of trigeminal ganglion neurons projecting to gingiva or tooth pulps in the lower jaw of the cichlid Tilapia mariae.

Rat trigeminal ganglion neurons projecting to the oral mucosa or to tooth pulps have different cell diameters and contain different chemical markers. In the present paper we examine whether trigeminal ganglion neurons sending axons to gingiva or tooth pulps in the lower jaw of the cichlid Tilapia mariae differ in a similar way. Retrograde tracing with fluorescent latex microspheres revealed labelled gingival and pulpal neurons in the caudal part of the trigeminal ganglion. The gingival neurons had a unimodal size distribution (peak 11 microns; range 8-14 microns) and the pulpal neurons exhibited a bimodal size distribution (peaks 12 and 25 microns; range 10-40 microns). Immunohistochemistry revealed a calcitonin gene-related peptide-like immunoreactivity in some 40% of the gingival neurons and a substance P-like immunoreactivity in 30%. Of the small pulpal neurons about 60% exhibited a calcitonin gene-related peptide-like immunoreactivity and 15% showed a substance P-like immunoreactivity. Of the large pulpal neurons some 70% exhibited a calcitonin gene-related peptide-like immunoreactivity. These neurons did not show a substance P-like immunoreactivity. In some animals a few trigeminal ganglion neurons showed a neuropeptide Y- or a vasoactive intestinal polypeptide-like immunoreactivity. Perikarya with a tyrosine hydroxylase- or a choline acetyl transferase-like immunoreactivity were not observed. We conclude that gingiva and tooth pulps in the lower jaw of T. mariae are innervated by trigeminal ganglion neurons, the cell diameters and neuropeptide contents of which differ in a pattern similar to that in the rat. Hence, this seems to represent a conserved evolutionary pattern.

Animals↗