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PubMed1992

Receptive field organization of retinal ganglion cells in the spastic mutant mouse.

1. We examined the receptive field properties of retinal ganglion cells in the isolated, superfused retinae of spastic mutant mice (B6C3Fe-spa/spa) that did not have the retinal degeneration (rd) phenotype. Glycine receptor density in the spastic mutant is greatly reduced in all areas of the CNS that have been examined. Phenotypically normal litter-mates were used as controls. Radial sections from the retinae of both spastic and normal animals were examined with light and electron microscopy and no differences were observed. The planimetric density of the cell bodies in the inner nuclear layer did not differ between the normal and mutant animals, about 400 cm-2. The absolute dark-adapted sensitivity of spastic ganglion cells was greater (271 +/- 69.0 impulses quanta-1 rod-1) than that of normal ganglion cells (47.7 +/- 10.4 impulses quanta-1 rod-1; P < 0.01). 2. Extracellular recordings of retinal ganglion cell responses to circular and annular stimuli, centred on the receptive field, were used to construct peri-stimulus-time histograms. In normal retinae, an annular stimulus elicited a response that was characteristic of the surround response mechanism of receptive fields with antagonistic centre-surround organization. In the mutant retina, annular stimuli did not elicit a surround-type response; instead, a centre-type response was recorded. 3. Illumination of the receptive field periphery attenuated centre-type responses in ganglion cells from both spastic and normal retinae. Centred circular stimuli of various areas (14, 35, 78, 122, 235, 783 deg2) were presented to the receptive fields. For mutant and normal ganglion cells, the response to the largest stimulus was smaller than that to an intermediate-sized stimulus. 4. The effect of strychnine, a glycine receptor antagonist, on the response to circular stimuli was examined. Very low concentrations of strychnine attenuated the light response in mutant retinae (apparent inhibitory binding constant KI = 8.1 x 10(-13) M). In normal animals, the light response was also attenuated by strychnine, but the apparent KI was much higher (apparent KI = 1 x 10(-7) M). 5. In normal ganglion cells, the sustained component of the light response was much more attenuated by strychnine than was the transient component. Interestingly, ganglion cells from spastic retinae did not exhibit a sustained component, even at stimulus luminances that evoked responses near threshold.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Ocular↗
PubMed1990

Cardiac responses to electrical stimulation of discrete loci in canine atrial and ventricular ganglionated plexi.

The purpose of the present study was to examine cardiac effects induced by electrical stimulation (1-4 V, 1 ms, 200 Hz) of discrete loci within the ganglionated plexi located on canine atria and ventricles. When 20 loci in the right atrial ventral ganglionated plexi of 11 anesthetized open-chest dogs were stimulated, bradycardia and/or right and left atrial force suppression occurred when, on average, 15% of these loci were stimulated. Bradycardia and atrial force suppression were elicited when, on average, 8% of 15 loci in the left atrial ventral ganglionated plexi of eight dogs was stimulated. When these loci were restimulated after acute decentralization, cardiac responses were attenuated or occasionally eliminated. After atropine (1 mg/kg iv) administration, repeat stimulation of loci in the right but not left atrial ganglionated plexus induced tachycardia. Stimulation of loci in the right ventricular ganglionated plexus after the subsequent administration of desipramine (1 mg/kg iv) in six dogs resulted in an increase in right ventricular conus intramyocardial pressure. After hexamethonium administration (10 mg/kg iv, followed by a continuous infusion of 1 mg.kg-1.min-1), sympathetic responses were no longer elicited from one of the five dogs in which loci in the right atrial ganglionated plexi and from two of the six dogs in which loci of the right ventricular ganglionated plexus had elicited responses. We conclude that atrial and ventricular ganglionated plexi contain efferent parasympathetic, efferent sympathetic, and afferent neurons.

Animals↗
PubMed1988

Bipolar origin of synaptic inputs to sustained OFF-ganglion cells in the mudpuppy retina.

1. The synaptic inputs to sustained OFF-center ganglion cells of the mudpuppy retina were studied using a superfused retina-eye-cup preparation. Intra- and extracellular electrophysiological recording techniques were carried out during bath application of 2-amino-4-phosphonobutyrate (APB), a glutamate analog that selectively blocks the light responses of ON-bipolars but has minor effects on OFF-bipolar or horizontal cells. 2. The use of APB reduced ganglion cell inputs to those arising from the OFF-bipolar channel. In this way, the existence and polarity (depolarizing vs. hyperpolarizing) of direct or indirect bipolar connections to ganglion cells was determined. 3. Cobalt application was used to block synaptic transmission and demonstrate that APB does not have a direct excitatory action on ganglion cells. 4. Intracellular recording experiments included the use of pulsatile and sustained current injection to evaluate the input resistance changes associated with light, the action of APB, and the excitatory, inhibitory, or disafacilitory nature of the postsynaptic potentials. 5. Some intracellularly recorded cells were stained with horseradish peroxidase (HRP) to verify the ganglion cell origin of the recordings. 6. The OFF-ganglion cell population of the mudpuppy appears to be a heterogeneous group of cells. Sustained OFF-ganglion cells can receive dominant inputs through either the ON- or OFF-bipolar cell pathway or through a mixture of the two. 7. Based on the analysis of this study, we divided sustained OFF-ganglion cells into three subclasses. For one class, light causes the removal of a sustained excitatory input which originates from the OFF-bipolar channel (i.e., a light-evoked disfacilitation); a second class of cells is almost entirely driven by the ON-bipolar channel through a sustained light-evoked inhibitory input; and a third class receives both a light-evoked sustained disfacilitory input from the OFF-bipolar channel and a sustained inhibitory input through the ON-bipolar pathway. Thus the retina appears to use a variety of mechanisms that result in a common response to flashing light stimuli. 8. The results of this study show that APB can be a powerful tool for pharmacologically deciphering the functional connections that exist between outer and inner retinal neurons.

Aminobutyrates↗
PubMed1988

Synaptic inputs and morphology of sustained ON-ganglion cells in the mudpuppy retina.

1. Sustained ON-ganglion cells from the mudpuppy retina were studied with a combined approach, including intracellular and extracellular recording from the superfused retina-eyecup preparation, pharmacology with bath-applied 2-amino-4-phosphonobutyrate (APB), and retrograde and intracellular staining using horse radish peroxidase (HRP). 2. Bath application of micromolar levels of APB selectively blocks the light response of ON-bipolar cells; APB was used to separate synaptic inputs into those which originate from ON- vs. OFF-bipolar cells. This approach clearly demonstrates that the light response of the vast majority of sustained ON-ganglion cells is primarily the result of sustained excitatory inputs that arise (directly or indirectly) from ON-bipolar cells. 3. APB revealed the presence of transient excitatory OFF-inputs in many sustained ON-ganglion cells that are normally not evident. 4. Five sustained ON-ganglion cells were intracellularly stained with HRP and their morphology was analyzed with the aid of a computer-assisted neuron reconstruction system. The stained cells are anatomically similar, based on quantitative analysis of a number of morphological parameters. The dendritic trees of all five cells are primarily confined to sublamina b of the inner plexiform layer, although some cells have a small number of processes that ramify in sublamina a. These latter processes may relate to the transient excitatory OFF-inputs revealed with APB application. 5. Ganglion cells which are morphologically similar to the stained, intracellularly sustained ON-ganglion cells were found in a collection of Golgi-like cells that were labeled by retrograde HRP transport. This raises the possibility that sustained ON-ganglion cells in the mudpuppy may constitute a morphologically identifiable class of retinal ganglion cells in this species. There is also some suggestion that a morphologically similar class of OFF-cells may be present.

Aminobutyrates↗
PubMed1995

Effects of Ca2+ channel blockers on directional selectivity of rabbit retinal ganglion cells.

1. Extracellular recordings were made from ON-OFF directionally selective ganglion cells in superfused rabbit retinas in order to examine the effects of voltage-activated Ca2+ channel blockers on the response of these ganglion cells to a moving bar of light. 2. Bath application of Cd2+ (67-110 microM) abolished directional selectivity in the ganglion cells. That is, the cells gave nearly equal responses to the leading and trailing edges of a bar of light moved in the preferred and null directions. This effect of Cd2+ was rapidly reversible. 3. Directional selectivity in the ganglion cells was not affected by Ni2+ (120-440 microM), Co2+ (180-690 microM), or the L-type Ca2+ channel blockers nicardipine (7-29 microM) and methoxyverapamil (18-60 microM). These blockers did, however, reduce the responses of the ganglion cells to a bar of light moved in the preferred direction. 4. omega-Conotoxin MVIIC (130 nM-1.9 microM), which potently blocks N-type and Q-type Ca2+ channels, abolished directional selectivity in the ganglion cells. omega-Conotoxin MVIIC not only brought out large leading and trailing edge responses to movement of a bar of light in the null direction, but it also increased the leading and trailing edge responses to movement of the bar of light in the preferred direction. The effect of omega-conotoxin MVIIC was slowly reversible. 5. The N-type Ca2+ channel blocker omega-conotoxin GVIA (1.4-6.3 microM) did not abolish directional selectivity in the ganglion cells. This blocker did, however, bring out some response to the leading edge of a bar of a light moved in the null direction. This effect of omega-conotoxin GVIA appeared to be irreversible. 6. omega-Agatoxin IVA, a potent blocker of P-type Ca2+ channels, when bath applied at low concentrations (66-83 nM), increased the responses to movement of a bar of light in the preferred direction but brought out only small responses to movement of the bar of light in the null direction. At high concentrations (250-280 nM) that reportedly block Q-type Ca2+ channels by > or = 50%, omega-agatoxin IVA nearly abolished directional selectivity. This effect of omega-agatoxin IVA was slowly reversible. 7. These results indicate that omega-conotoxin MVIIC- and omega-agatoxin IVA-sensitive Ca2+ channels (possibly Q-type channels) play an important role in the generation of directional selectivity in rabbit retinal ganglion cells.

Action Potentials↗
PubMed1997

Decoding visual information from a population of retinal ganglion cells.

Decoding visual information from a population of retinal ganglion cells. J. Neurophysiol. 78: 2336-2350, 1997. This work investigates how a time-dependent visual stimulus is encoded by the collective activity of many retinal ganglion cells. Multiple ganglion cell spike trains were recorded simultaneously from the isolated retina of the tiger salamander using a multielectrode array. The stimulus consisted of photopic, spatially uniform, temporally broadband flicker. From the recorded spike trains, an estimate was obtained of the stimulus intensity as a function of time. This was compared with the actual stimulus to assess the quality and quantity of visual information conveyed by the ganglion cell population. Two algorithms were used to decode the spike trains: an optimized linear filter in which each action potential made an additive contribution to the stimulus estimate and an artificial neural network trained by back-propagation to match spike trains with stimuli. The two methods performed indistinguishably, suggesting that most of the information about this stimulus can be extracted by linear operations on the spike trains. Individual ganglion cells conveyed information at a rate of 3.2 +/- 1.7 bits/s (mean +/- SD), with an average information content per spike of 1.6 bits. The maximal possible rate of information transmission compatible with the measured spiking statistics was 13.9 +/- 6.3 bits/s. On average, ganglion cells used 22% of this capacity to encode visual information. When a decoder received two spike trains of the same response type, the reconstruction improved only marginally over that obtained from a single cell. However, a decoder using an ON and an OFF cell extracted as much information as the sum of that obtained from each cell alone.Thus cells of opposite response type encode different and nonoverlapping features of the stimulus. As more spike trains were provided to the decoder, the total information rate rapidly saturated, with 79% of the maximal value obtained from a local cluster of just four neurons of different functional types. The decoding filter applied to a given neuron's spikes within such a multiunit decoder differed substantially from the filter applied to that same neuron in a single-unit decoder. This shows that the optimal interpretation of a ganglion cell's action potential depends strongly on the simultaneous activity of other nearby cells. The quality of the stimulus reconstruction varied greatly with frequency: flicker components below 1 Hz and above 10 Hz were reconstructed poorly, and the performance was optimal near 2.5 Hz. Further analysis suggests that temporal encoding by ganglion cell spike trains is limited by slow phototransduction in the cone photoreceptors and a corrupting noise source proximal to the cones.

Action Potentials↗
PubMed1999

Correlated firing in rabbit retinal ganglion cells.

A ganglion cell's receptive field is defined as that region on the retinal surface in which a light stimulus will produce a response. While neighboring ganglion cells may respond to the same stimulus in a region where their receptive fields overlap, it generally has been assumed that each cell makes an independent decision about whether to fire. Recent recordings from cat and salamander retina using multiple electrodes have challenged this view of independent firing by showing that neighboring ganglion cells have an increased tendency to fire together within +/-5 ms. However, there is still uncertainty about which types of ganglion cells fire together, the mechanisms that produce coordinated spikes, and the overall function of coordinated firing. To address these issues, the responses of up to 80 rabbit retinal ganglion cells were recorded simultaneously using a multielectrode array. Of the 11 classes of rabbit ganglion cells previously identified, coordinated firing was observed in five. Plots of the spike train cross-correlation function suggested that coordinated firing occurred through two mechanisms. In the first mechanism, a spike in an interneuron diverged to produce simultaneous spikes in two ganglion cells. This mechanism predominated in four of the five classes including the ON brisk transient cells. In the second mechanism, ganglion cells appeared to activate each other reciprocally. This was the predominant pattern of correlated firing in OFF brisk transient cells. By comparing the receptive field profiles of ON and OFF brisk transient cells, a peripheral extension of the OFF brisk transient cell receptive field was identified that might be produced by lateral spike spread. Thus an individual OFF brisk transient cell can respond both to a light stimulus directed at the center of its receptive field and to stimuli that activate neighboring OFF brisk transient cells through their receptive field centers.

Action Potentials↗
PubMed1993

The visual system of the Florida garfish, Lepisosteus platyrhincus (Ginglymodi). III. Retinal ganglion cells.

The vitreal vascularization, optic nerve fiber layer and the retinal ganglion cells are examined in the Florida garfish, one of the two surviving genera of the ginglymode group of actinopterygian fishes. In the absence of a choroidal gland, a well developed system of hyaloid blood vessels overlie the inner retina. The optic nerve fiber and ganglion cell layers are integrated to form a series of alternating columns or fascicles emanating from an elongated optic nerve head. Horseradish peroxidase or cobaltous lysine infusion from the optic nerve reveals seven ganglion cell classes based on soma size and position, dendritic field size, retinal coverage and terminal stratification. Two discrete populations of giant ganglion cells with large somata and large dendritic fields stratify either within the sclerad region (type I cells) and/or within the middle region (type 2 cells) of the inner plexiform layer. Both giant ganglion cell populations (1% of total) form evenly distributed arrays with the dendritic arbor of each type covering the retina completely. Between seven and nine type 2 cells overlap the dendritic field of a single type 1 cell. Type 3 cells are small and located in the inner nuclear layer with a multistratified dendritic field terminating throughout the inner plexiform layer. Topographic analysis of the population of type 3 cells (4% of total) reveals a temporal area centralis (6.25 x 10(2) cells per mm2) and a ventral horizontal streak (6.25 x 10(2) cells per mm2). The large population of cells within the ganglion cell layer are classified as types 4, 5 and 6 based on soma size, dendritic field size and dendritic stratification and collectively these cells match the distribution of ganglion cells within the inner nuclear layer with 5.3 x 10(3) cells per mm2 in the temporal area centralis and 8.6 x 10(3) cells per mm2 in the horizontal streak. Type 7 cells possess small somata and send branches into both the inner and outer plexiform layers and have been termed biplexiform ganglion cells. Phylogenetic comparisons of several morphological features of the garfish retina reveals the polarity, conservation and the evolution of a number of visual characters.

Animals↗
PubMed2005

Effect of cochlear implantation on residual spiral ganglion cell count as determined by comparison with the contralateral nonimplanted inner ear in humans.

It is generally assumed that at least a minimal number of spiral ganglion cells is essential for successful speech perception with a cochlear implant. Although the insertion of a multichannel cochlear implant frequently results in loss of residual hearing in the implanted ear, this outcome does not imply that significant damage to residual populations of spiral ganglion cells has occurred. The purpose of the current study was to compare spiral ganglion cell counts in implanted and nonimplanted cochleas in 11 patients for whom both temporal bones were available and in whom a multichannel cochlear implant had been placed unilaterally. The temporal bones were processed for light microscopy by standard techniques. The cochleas were reconstructed by 2-dimensional methods. Spiral ganglion cell counts of the implanted and nonimplanted sides were compared by a paired t-test (2-tailed). The mean spiral ganglion cell counts for implanted and nonimplanted ears were not statistically different in the most basal three segments of the cochlea. However, the mean spiral ganglion cell count in segment 4 (apical segment) and the mean total spiral ganglion cell count were lower in the implanted cochleas than in the nonimplanted cochleas (p < .01). The results of this study suggest a modest decrease in the total spiral ganglion cell count in the implanted ears as compared to the nonimplanted ears, principally in the apical segment. Possible interpretations of this finding are discussed.

Aged↗
PubMed2006

Progressive ganglion cell loss and optic nerve degeneration in DBA/2J mice is variable and asymmetric.

BACKGROUND: Glaucoma is a chronic neurodegenerative disease of the retina, characterized by the degeneration of axons in the optic nerve and retinal ganglion cell apoptosis. DBA/2J inbred mice develop chronic hereditary glaucoma and are an important model system to study the molecular mechanisms underlying this disease and novel therapeutic interventions designed to attenuate the loss of retinal ganglion cells. Although the genetics of this disease in these mice are well characterized, the etiology of its progression, particularly with respect to retinal degeneration, is not. We have used two separate labeling techniques, post-mortem DiI labeling of axons and ganglion cell-specific expression of the betaGeo reporter gene, to evaluate the time course of optic nerve degeneration and ganglion cell loss, respectively, in aging mice. RESULTS: Optic nerve degeneration, characterized by axon loss and gliosis is first apparent in mice between 8 and 9 months of age. Degeneration appears to follow a retrograde course with axons dying from their proximal ends toward the globe. Although nerve damage is typically bilateral, the progression of disease is asymmetric between the eyes of individual mice. Some nerves also exhibit focal preservation of tracts of axons generally in the nasal peripheral region. Ganglion cell loss, as a function of the loss of betaGeo expression, is evident in some mice between 8 and 10 months of age and is prevalent in the majority of mice older than 10.5 months. Most eyes display a uniform loss of ganglion cells throughout the retina, but many younger mice exhibit focal loss of cells in sectors extending from the optic nerve head to the retinal periphery. Similar to what we observe in the optic nerves, ganglion cell loss is often asymmetric between the eyes of the same animal. CONCLUSION: A comparison of the data collected from the two cohorts of mice used for this study suggests that the initial site of damage in this disease is to the axons in the optic nerve, followed by the subsequent death of the ganglion cell soma.

Age Factors↗
PubMed1997

Reggie-1 and reggie-2, two cell surface proteins expressed by retinal ganglion cells during axon regeneration.

Fish--in contrast to mammals--regenerate retinal ganglion cell axons when the optic nerve is severed. Optic nerve injury leads to reexpression of proteins, which typically are first expressed in newly differentiated retinal ganglion cells and axons. Here we identified two new proteins of fish retinal ganglion cells, reggie-1 and reggie-2, with monoclonal antibody M802 and molecular cloning techniques. In normal fish, M802 stained the few retinal axons derived from newborn ganglion cells which in fish are added lifelong to the retinal margin. After optic nerve injury, however, M802 labeled all retinal ganglion cells and retinal axons throughout their path into tectum. Consistent with M802 staining, reggie-1 and reggie-2 mRNAs were present in lesioned retinal ganglion cells, as demonstrated by in situ hybridization, but were not detectable in their normal mature counterparts. In western blots with membrane proteins of the adult goldfish brain, M802 recognizes a 48x10(3) Mr protein band. At the amino acid level, 48x10(3) Mr reggie-1 and reggie-2 are 44% identical, lack transmembrane and membrane anchor domains, but appear membrane associated by ionic interactions. Reggie-1 and reggie-2 are homologous to 35x10(3) Mr ESA (human epidermal surface antigen) but are here identified as neuronal surface proteins, present on newly differentiated ganglion cells at the retinal margin and which are reexpressed in mature ganglion cells upon injury and during axonal regeneration.

Amino Acid Sequence↗
PubMed2002

Brn3b/Brn3c double knockout mice reveal an unsuspected role for Brn3c in retinal ganglion cell axon outgrowth.

In mice, Brn3 POU domain transcription factors play essential roles in the differentiation and survival of projection neurons within the retina, inner ear, dorsal root and trigeminal ganglia. During retinal ganglion cell differentiation, Brn3b is expressed first, followed by Brn3a and Brn3c. Targeted deletion of Brn3b, but not Brn3a or Brn3c, leads to a loss of most retinal ganglion cells before birth. However, as a few retinal ganglion cells are still present in Brn3b(-/-) mice, Brn3a and Brn3c may partially compensate for the loss of Brn3b. To examine the role of Brn3c in retinal ganglion cell development, we generated Brn3b/Brn3c double knockout mice and analyzed their retinas and optic chiasms. Retinal ganglion cell axons from double knockout mice were more severely affected than were those from Brn3b-deficient mice, indicating that Brn3c was required for retinal ganglion cell differentiation and could partially compensate for the loss of Brn3b. Moreover, Brn3c had functions in retinal ganglion cell differentiation separate from those of Brn3b. Ipsilateral and misrouted projections at the optic chiasm were overproduced in Brn3b(-/-) mice but missing were entirely in optic chiasms of Brn3b/Brn3c double knockout mice, suggesting that Brn3c controlled ipsilateral axon production. Forced expression of Brn3c in Brn3b(-/-) retinal explants restored neurite outgrowth, demonstrating that Brn3c could promote axon outgrowth in the absence of Brn3b. Our results reveal a complex genetic relationship between Brn3b and Brn3c in regulating the retinal ganglion cell axon outgrowth.

Animals↗
PubMed1989

[Distribution of retinal ganglion cells projecting into the nucleus of the optic tract in the rat].

Recent neurophysiological studies have disclosed that the nucleus of the optic tract (NOT) in the pretectum is the first relay station responsible for horizontal optokinetic nystagmus (OKN) both in non-foveate and foveate animals. However, what parts of the retina and what kinds of retinal ganglion cells project their fibers into the NOT have been controversial. In the present study, horseradish peroxidase conjugated with wheatgerm agglutinin (WGA-HRP) was injected into the NOT of rats. The retina and injection sites were processed for the histochemical demonstration of WGA-HRP in order to investigate the distribution of the retinal ganglion cells projecting into the NOT. The present study indicated that visual signals responsible for OKN are mainly conducted from the contralateral retinal ganglion cells, and only from the ventral area of the ipsilateral retina. The retinal ganglion cells projecting into the NOT ipsilateral to the injection site were larger than those on the contralateral side. Large retinal ganglion cells existed on the peripheral areas including ipsilateral ventral area. The density of the ventral ganglion cells of the retina contralateral to the injection site was lower than that in other areas of retina, and the density of the ventral ganglion cells ipsilateral to the injection site tented to be greater than that on the contralateral side. Since the ventral area of retina corresponded to the upper visual field in front of the nose, it may receive visual signal of OKN and fire OKN. In conclusion, visual signals responsible for OKN are conducted through the retinal ganglion cells mainly contralaterally, and only from the ventral area of the retina ipsilateral to the injection site.

Animals↗
PubMed2001

Neuroprotection of retinal ganglion cells by brimonidine in rats with laser-induced chronic ocular hypertension.

PURPOSE: To examine the neuroprotective effect of the alpha(2)-adrenergic agonist brimonidine in a chronic ocular hypertension model. METHODS: Intraocular pressure (IOP) was elevated by laser photocoagulation of episcleral and limbal veins. Retinal ganglion cell loss was evaluated in wholemounted retinas. Brimonidine or timolol was administered, either at the time of or 10 days after IOP elevation and continued for 3 weeks. Drug-related immunohistochemical changes in glial fibrillary acidic protein (GFAP) were also determined after 3 weeks. RESULTS: Laser treatment caused a twofold IOP increase over baseline that was maintained for 2 months. A time-dependent loss of ganglion cells occurred with elevated IOP. Systemic administration of brimonidine or timolol caused little decrease in IOP. After 3 weeks of elevated IOP, ganglion cell loss in control rats was 33% +/- 3%. Brimonidine reduced the progressive loss of ganglion cells to 26% +/- 1% and 15% +/- 2% at doses of 0.5 and 1 mg/kg. d, respectively. Timolol had no effect. Ten days of high IOP resulted in 22% +/- 4% ganglion cell loss. Brimonidine administration initiated 10 days after IOP elevation prevented any further loss of ganglion cells. In vehicle- or timolol-treated rats, ganglion cell loss continued to 33%. The increase in immunoreactivity of GFAP in ocular hypertensive retinas was attenuated by brimonidine. CONCLUSIONS: Systemic application of brimonidine or timolol had little effect on IOP. Brimonidine, but not timolol, showed significant protection of retinal ganglion cells when applied at the time of IOP elevation and prevented further cell loss when applied after IOP was elevated. This indicates that brimonidine has a neuroprotective activity unrelated to its effect on ocular hypotension.

Adrenergic alpha-Agonists↗
PubMed2003

[The effect of SP-8-CPT-cAMP on the tracer coupling between the retinal ganglion cells and amacrine cells].

PURPOSE: To study the effect of SP-8-CPT-cAMP on the tracer coupling between the retinal ganglion cells and amacrine cells in rabbits. METHODS: The retinas of rabbit were cultured and treated with SP-8-CPT-cAMP .4% neurobiotin was injected into retinal single OFF-alpha ganglion cell with micro-injection, following tissue fixation with 4% paraformaldehyde, Cells were visualized with 1:600 streptavidin-Cy3. The intensity of tracer diffusing through the gap junctions among the ganglion cells and amacrine cells was calculated with confocal microscope. RESULTS: In the dendritic field of injected ganglion cells and cross the field some other ganglion cells(G1) and amacrine cells locating in the inner nuclear layer were stained. Two types of amacrine cells: brighter one (A1) and dimmer one (A2) were found. The intensity of neurobiotin in coupled G1,A1,A2 after treated with SP-8-CPT-cAMP is much higher than that of the untreated retinas. CONCLUSION: The gap junctions exist among the OFF-alpha ganglion cells and between OFF-alpha ganglion cells and amacrine cells. SP-8-CPT-cAMP increases the permeability of gap junction in OFF-alpha ganglion cell network.

Amacrine Cells↗
PubMed1992

Trigeminal ganglion cell processes are spatially ordered prior to the differentiation of the vibrissa pad.

The rodent trigeminal system is characterized by the punctate organization of its afferents and neurons that replicate the distribution of mystacial vibrissae and sinus hairs on the snout. We have examined the development of topographic equivalence between the sensory periphery on the snout and the brainstem trigeminal nuclei in rats. Lipophilic tracers Dil (1,1'-dioctodecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate) and DiA [4-(4-dihexadecylaminostyryl)-N-methylpyridinium iodide] were used to label trigeminal ganglion cells and their processes differentially from discrete regions of the presumptive vibrissa field in fixed embryos. Our results show that trigeminal ganglion cell processes are spatially ordered as they reach their peripheral and central targets on embryonic day 12 (E12). Peripheral processes of dorsomedially situated ganglion cells course dorsally toward the presumptive vibrissa field, and those of ventrolaterally situated ganglion cells project ventrally. On E13, the central processes of dorsomedially situated ganglion cells enter the brainstem medially whereas those of ventrolaterally situated ganglion cells enter laterally. This spatial order of trigeminal ganglion cell processes precedes the emergence of vibrissa rows in the periphery and the differentiation of brainstem trigeminal nuclei. Thus, the subsequent transfer of the vibrissa-related pattern to the brainstem trigeminal nuclei occurs along a preexisting, spatially aligned bridge formed by the trigeminal ganglion cells.

Animals↗
PubMed1991

The neurons of the retinal ganglion cell layer of the guinea pig: quantitative analysis of their distribution and size.

1. The topographical distribution of ganglion cells and displaced amacrine cells in the guinea pig retina is described. 2. Neurons were counted in the ganglion cell layer of retinal whole mounts stained by the method of Nissl or retrogradely labeled with horseradish peroxidase. Neuronal soma size was estimated from samples taken from different retinal regions. 3. We estimate that a total of 295,000 neurons comprise the guinea pig ganglion cell layer and they consist of 159,000 ganglion cells and 136,000 displaced amacrine cells. 4. The visual streak is poorly differentiated. Ganglion cell density reaches a peak of 2,272 cells/mm2 in a temporal expansion of the visual streak, 4-5 mm toward the optic disk. The visual streak temporal expansion may represent the analogue of the area centralis for this species. The ventral hemi-retina has a higher ganglion cell density than the dorsal hemi-retina. The displaced amacrine cells are more uniformly distributed than the ganglion cells. 5. The present paper provides relevant data concerning the number and distribution of the neurons of the retinal ganglion cell which were not available or were very contradictory in the literature.

Animals↗
PubMed1991

Ganglion cell populations in labyrinthitis ossificans.

Ossification of the perilymphatic spaces of the inner ear is frequently found in patients with profound deafness who may be candidates for cochlear implantation. The ossification may be a hindrance in electrode insertion and has previously been considered a relative contraindication to implantation. The quantity of peripheral auditory elements remaining in a series of patients with labyrinthitis ossificans has not been reviewed. We performed a histopathologic study of 16 temporal bones with partial cochlear ossification of multiple etiologies. The organ of Corti and spiral ganglion were graphically reconstructed. The degree of obstruction was estimated for each millimeter of the scala tympani and scala vestibuli. A quantitative evaluation of the sensorineural elements of the inner ear (spiral ganglion cells, inner and outer hair cells, and peripheral auditory axons) was performed. The results were compared with 16 control patients with normal hearing and no evidence of cochlear ossification. Our results show that the greatest amount of damage is found in the organ of Corti with preservation of a significant number of spiral ganglion cells in most cases. A wide range of ganglion cells (6,310 to 28,196) was found in patients with labyrinthitis ossificans with the mean number of ganglion cells being 17,152. A profound sensorineural hearing loss was noted in all patients except one. Meningogenic labyrinthitis and otosclerosis were associated with the greatest loss of ganglion cells. The location of ossification could be correlated with the region showing loss of the organ of Corti. In the majority of patients, the location of ossification and fibrosis could not be correlated with the region of the spiral ganglion showing loss of ganglion cells. The implications of these findings for cochlear implantation is discussed.

Adolescent↗