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PubMed1988

Distribution of synaptic inputs onto goldfish retinal ganglion cell dendrites.

Retinal ganglion cells in the goldfish were labeled by retrograde transport of horseradish peroxidase, and areas near the optic disk where the dendrites appeared to be completely filled were analyzed by electron microscopy. Only 6% of their inputs were ribbon synapses from bipolar cells; the other 94% of the inputs were conventional synapses mostly or entirely from amacrine cells. There were three strata of the inner plexiform layer with high densities of inputs to ganglion cells, the first centered at approx. 50% and the second at approx. 80% of the inner plexiform layer depth, as measured from the ganglion cell layer to the inner nuclear layer. These two strata comprised 25% of the volume but contained 41% of the inputs to ganglion cells. There were also two strata with very low densities of ganglion cell inputs located near the boundaries of the inner plexiform layer, from 0- to 15% and 90- to 100% of the depth. These strata, which also comprised 25% of the volume, contained only 7% of the inputs to retinal ganglion cells. These strata near the boundaries of the inner plexiform layer also contained 81% of the processes with large, dense-cored vesicles characteristic of peptidergic neurons. We concluded that each of the two sublaminae, a and b, identified previously by physiological criteria, could be further divided into at least two strata, one near the boundary of the inner plexiform layer with abundant peptidergic terminals and very few ganglion cell synapses and another near the center of the inner plexiform layer with numerous ganglion cell synapses. We also propose a hypothesis that could explain the functions of these additional strata.

Animals↗
PubMed2003

Intravitreal injections of neurotrophic factors and forskolin enhance survival and axonal regeneration of axotomized beta ganglion cells in cat retina.

Some retinal ganglion cells in adult cats survive axotomy for two months and regenerate their axons when a peripheral nerve is transplanted to the transected optic nerve. However, regenerated retinal ganglion cells were fewer than 4% of the total retinal ganglion cell population in the intact retina. The present study examined the effects of intravitreal injections of neurotrophic factors (brain-derived neurotrophic factor, ciliary neurotrophic factor, basic fibroblast growth factor, glial cell-derived neurotrophic factor, neurotrophin 4), first on the survival of axotomized cat retinal ganglion cells within 2 weeks, and then on axonal regeneration of the retinal ganglion cells for 2 months after peripheral nerve transplantation. We tested first enhancement of the survival by one of the factors, and then one or two of them supplemented with forskolin, which increases intracellular cAMP. Single injections of 0.5 microg or 1 microg brain-derived neurotrophic factor, 1 microg ciliary neurotrophic factor, or 1 microg glial cell-derived neurotrophic factor significantly increased total numbers of surviving retinal ganglion cells; 1.6-1.8 times those in control retinas. Identification of retinal ganglion cell types with Lucifer Yellow injections revealed that the increase of surviving beta cells was most conspicuous: 2.5-fold (brain-derived neurotrophic factor) to 3.6-fold (ciliary neurotrophic factor). A combined injection of 1 microg brain-derived neurotrophic factor, 1 microg ciliary neurotrophic factor, and 0.1 mg forskolin resulted in a 4.7-fold increase of surviving beta cells, i.e. 50% survival on day 14. On the axonal regeneration by peripheral nerve transplantation, a combined injection of brain-derived neurotrophic factor, ciliary neurotrophic factor, and forskolin resulted in a 3.4-fold increase of beta cells with regenerated axons. The increase of regenerated beta cells was mainly due to the enhancing effect of neurotrophic factors on their survival, and possibly to a change of retinal ganglion cell properties by cAMP to facilitate their axonal regeneration.

Animals↗
PubMed1999

Organization of geniculate and trigeminal ganglion cells innervating single fungiform taste papillae: a study with tetramethylrhodamine dextran amine labeling.

Single gustatory nerve fibers branch and innervate several taste buds. In turn, individual taste buds may receive innervation from numerous gustatory nerve fibers. To evaluate the pattern of sensory innervation of fungiform papilla-bearing taste buds, we used iontophoretic fluorescent injection to retrogradely label the fibers that innervate single taste papillae in the hamster. For each animal, a single taste papilla was injected through the gemmal pore with 3.3% tetramethylrhodamine dextran amine. Fungiform papillae either at the tongue tip (0.5-1.5 mm from the tip) or more posteriorly (1.5-3.0 mm from the tip) were injected. After one to seven days survival, the geniculate and trigeminal ganglia and the tongue were sectioned and examined for labeled cells and fibers, respectively. Analysis of the number and topographic distribution of geniculate cells innervating single taste papillae, shows that: (i) 15 +/- 4 (S.D.) ganglion cells converge to innervate a single fungiform taste bud; (ii) more ganglion cells innervate anterior- (range: 13-35 cells) than posterior-lying buds (range: five to 12 cells), which, in part, may be related to bud volume (microm3); and (iii) ganglion somata innervating a single taste bud are scattered widely within the geniculate ganglion. Analysis of labeled fibers in the tongue demonstrated that two to eight taste buds located within 2 mm of the injected taste bud share collateral innervation with the injected taste bud. Since all buds with labeled fibers were located in close proximity (within a 2-mm radius), widely dispersed geniculate ganglion cells converge to innervate closely spaced fungiform taste buds. Trigeminal ganglion (mandibular division) cells were also labeled in every case and, as with the geniculate ganglion, a dispersed cell body location and collateralization pattern among papillae were observed. This study shows that iontophoresis of tetramethylrhodamine dextran amine, selectively applied to individual peripheral receptor end-organs, effectively locates sensory ganglion cells in two different ganglia that project to these sites. Moreover, the marker demonstrates collateral branches of sensory afferents associated with the labeled fibers and the nearby receptor areas innervated by these collaterals. The labeling of single or clusters of receptor cells, as well as identified sensory afferents, affords future possibilities for combining this technique with immunocytochemistry to establish the relationships of innervation patterns with neurotransmitters and neurotropic substances within identified cells.

Afferent Pathways↗
PubMed1999

Ciliary neurotrophic factor promotes the regrowth capacity but not the survival of intraorbitally axotomized retinal ganglion cells in adult hamsters.

Ciliary neurotrophic factor has recently been shown to promote the axonal regrowth of retinal ganglion cells into a peripheral nerve graft following an intracranial transection of the optic nerve (approximately 7 mm from the optic disc). It is unclear whether the enhancement of axonal regrowth by ciliary neurotrophic factor application correlates with the enhancement of survival of retinal ganglion cells and/or the up-regulation of expression of growth-associated protein-43 messenger RNA in retinas. The present study evaluated the regenerative capacity of retinal ganglion cells following intraorbital transection of the optic nerve (approximately 1.5 mm from the optic disc) and the attachment of a peripheral nerve to the ocular stump of the optic nerve. In addition, we have determined the survival of retinal ganglion cells and the expression of growth-associated protein-43 messenger RNA in ciliary neurotrophic factor-treated retinas following optic nerve transection. The results showed that in the ciliary neurotrophic factor-treated retinas, the number of retinal ganglion cells which had regrown axons into a peripheral nerve is about four times more than the control. In the axotomized retinas, ciliary neurotrophic factor initiated sprouting of axon-like processes at 14 and 28 days post-axotomy and up-regulated the expression level of growth-associated protein-43 messenger RNA at 7, 14 and 28 days post-axotomy. However, ciliary neurotrophic factor did not prevent the death of axotomized retinal ganglion cells. We suggest that one possible mechanism for the axonal regeneration of axotomized retinal ganglion cells by ciliary neurotrophic factor could be mediated by the up-regulation of growth-associated protein-43 gene expression and not by increasing the pool of surviving retinal ganglion cells after axotomy.

Animals↗
PubMedDate not supplied

The role of NMDA and non-NMDA excitatory amino acid receptors in the functional organization of primate retinal ganglion cells.

The role of excitatory amino acid (EAA) receptors in primate retinal ganglion cell function was analyzed in a superfused retina-eyecup preparation using single-unit, extracellular recording techniques. The effects of bath applied L-2-amino-4-phosphonobutyrate (APB), N-methyl-D-aspartate (NMDA), and non-NMDA EAA receptor agonists and antagonists were examined on the light-evoked responses and resting firing rates of ganglion cells. APB (30-100 microM) reduced or blocked the light-evoked responses and resting firing rates of all ON-center ganglion cells; higher doses of APB (100 microM) were required to block the light-evoked responses of ON-transient cells. In contrast, an increase in resting firing rates was observed when L-APB was applied to some OFF-center ganglion cells. The EAA agonists kainate (KA) (10-20 microM) and NMDA (200-350 microM) increased the firing rate of virtually all ganglion cells examined. Quisqualate (10-20 microM) increased firing in most cells, but occasionally (4/13 cases) produced inhibition. The NMDA antagonist D-amino-phosphono-heptanoic acid (D-AP7) (200-250 microM) reduced the light-evoked responses of ganglion cells by an average of 12% from control levels, while resting firing rates declined 37%. In the presence of D-AP7, the basic receptive-field characteristics of cells were not significantly altered. In contrast, two non-NMDA receptor antagonists, NBQX (2,3-Dihydroxy-6-nitro-7-sulfamoyl-benzo-(F)-quinoxalinedione) and DNQX (6,7-dinitro-quinoxaline-2,3-dione), produced substantial reductions in the light-evoked responses (82%) and resting firing rates (87%) of all ganglion cell classes. A striking observation in some neurons was the recovery of a persistent transient light-evoked response in the presence of NBQX. This NBQX-insensitive, light-evoked response was always blocked by adding D-AP7. Thus, neurotransmission from bipolar to ganglion cells in primates is mediated predominantly by non-NMDA EAA receptors, with NMDA receptors forming a minor component of the light-evoked response.

Aminobutyrates↗
PubMed1989

Microtubule-associated protein 1A (MAP 1A) is a ganglion cell marker in adult rat retina.

We have used antibodies raised against a cytoskeletal protein, microtubule-associated protein 1A (MAP 1A), to stain adult rat retina. In cryostat and polyethylene glycol-embedded radial sections, the fiber layer, ganglion cell layer, and inner plexiform layer were highly immunoreactive, a finding that suggested that the ganglion cell somata, axons, and dendrites were recognized by these antibodies. Retrograde labeling of retinal cell somata from the superior colliculus and dorso-lateral geniculate nucleus to identify ganglion cells showed colocalization of the tracer and immunoreactive cells. Double labeling with nuclear stains revealed that many cells in the ganglion cell layer, which are likely displaced amacrine cells, were not recognized by these antibodies. Furthermore, transection of ganglion cell axons, a procedure that causes retrograde degeneration of many of the axotomized ganglion cells, led to a decrease in the number of anti-MAP 1A immunoreactive cells in retinal wholemounts. Thus, MAP 1A antibodies preferentially stain ganglion cell somata and dendrites but not amacrine cells. These antibodies should be useful ganglion cell markers.

Animals↗
PubMedDate not supplied

Effects of serotonergic agonists and antagonists on ganglion cells in the goldfish retina.

Extracellular recordings were made from the isolated goldfish retina during superfusion with various serotonergic agonists and antagonists to determine the effects of these drugs on the maintained activity and response properties of the ganglion cells. Superfusion of the retina with serotonin (25-500 microM) increased the maintained activity of OFF-center ganglion cells and decreased the maintained activity of ON-center ganglion cells. In addition, serotonin also attenuated the excitatory responses to annular stimuli, suggesting a decrease in the strength of surround input to the ganglion cells. The effects of serotonin on OFF-center ganglion cells were mimicked by the nonselective 5-HT1 agonist 5-MeOT and the 5-HT1A receptor agonist 8-OH-DPAT, while only 5-MeOT mimicked the action of serotonin on ON-center ganglion cells. The effects of exogenously applied serotonin on the ganglion cells could be blocked by the mixed 5-HT1/5-HT2 receptor antagonist methysergide but not by the 5-HT2 receptor antagonist mianserin or the dopamine receptor antagonist haloperidol. These results support previous anatomical and biochemical evidence that serotonin functions in a neurotransmitter or neuromodulatory role in the teleost retina and suggest that serotonin may be involved in modulating the maintained activity and surround input to the ganglion cells. The results also indicate that two different types of receptors may mediate the actions of serotonin in the ON and OFF pathways, respectively.

Animals↗
PubMedDate not supplied

Rabbit retinal ganglion cell responses mediated by alpha-bungarotoxin-sensitive nicotinic acetylcholine receptors.

The responses of many ganglion cells in the rabbit retina are mediated, at least in part, by acetylcholine (ACh) acting on neuronal nicotinic acetylcholine receptors (nAChRs). nAChRs are comprised of alpha and beta subunits; three beta subunits and nine alpha subunits of nAChRs have been identified and these subunits can combine to form a large number of functionally distinct nAChR subtypes. We examined the effects of cholinergic agents on the light-evoked responses of ganglion cells to determine which nAChR subtypes mediate the effects of ACh. Extracellular recordings of retinal ganglion cells were made in intact everted eyecup preparations and nicotinic agonists and antagonists were added to the superfusate. While several ganglion cell classes exhibited methyllycaconitine (MLA) sensitivity, the directionally selective (DS) ganglion cells were most sensitive; exposure to 30 nanomolar MLA, a concentration reportedly too low to affect alphaBgt-insensitive nAChRs, suppressed the stimulus-evoked responses of DS cells without eliminating directional selectivity. Epibatidine, which at low concentrations is an agonist selective for alphaBgt-insensitive nAChRs, stimulated firing of various cell types including DS ganglion cells at low nanomolar concentrations. The effects of the various agents tested persisted under cobalt-induced synaptic blockade. The low nanomolar MLA and epibatidine sensitivity of DS cells suggests that DS ganglion cells express both alphaBgt-sensitive and alphaBgt-insensitive nAChRs. Other ganglion cell types appear to express only alphaBgt-sensitive nAChRs but not alphaBgt-insensitive nAChRs.

Aconitine↗
PubMed1995

An alternative pathway for signal flow from rod photoreceptors to ganglion cells in mammalian retina.

Rod signals in the mammalian retina are thought to reach ganglion cells over the circuit rod-->rod depolarizing bipolar cell-->AII amacrine cell-->cone bipolar cells-->ganglion cells. A possible alternative pathway involves gap junctions linking the rods and cones, the circuit being rod-->cone-->cone bipolar cells-->ganglion cells. It is not clear whether this second pathway indeed relays rod signals to ganglion cells. We studied signal flow in the isolated rabbit retina with a multielectrode array, which allows the activity of many identified ganglion cells to be observed simultaneously while the preparation is stimulated with light and/or exposed to drugs. When transmission between rods and rod depolarizing bipolar cells was blocked by the glutamate agonist 2-amino-4-phosphonobutyric acid (APB), rod input to all On-center and briskly responding Off-center ganglion cells was dramatically reduced as expected. Off responses persisted, however, in Off-center sluggish and On-Off direction-selective ganglion cells. Presumably these responses were generated by the alternative pathway involving rod-cone junctions. This APB-resistant pathway may carry the major rod input to Off-center sluggish and On-Off direction-selective ganglion cells.

Aminobutyrates↗
PubMed2001

The Ath5 proneural genes function upstream of Brn3 POU domain transcription factor genes to promote retinal ganglion cell development.

During retinogenesis, the Xenopus basic helix-loop-helix transcription factor Xath5 has been shown to promote a ganglion cell fate. In the developing mouse and chicken retinas, gene targeting and overexpression studies have demonstrated critical roles for the Brn3 POU domain transcription factor genes in the promotion of ganglion cell differentiation. However, the genetic relationship between Ath5 and Brn3 genes is unknown. To understand the genetic regulatory network(s) that controls retinal ganglion cell development, we analyzed the relationship between Ath5 and Brn3 genes by using a gain-of-function approach in the chicken embryo. We found that during retinogenesis, the chicken Ath5 gene (Cath5) is expressed in retinal progenitors and in differentiating ganglion cells but is absent in terminally differentiated ganglion cells. Forced expression of both Cath5 and the mouse Ath5 gene (Math5) in retinal progenitors activates the expression of cBrn3c following central-to-peripheral and temporal-to-nasal gradients. As a result, similar to the Xath5 protein, both Cath5 and Math5 proteins have the ability to promote the development of ganglion cells. Moreover, we found that forced expression of all three Brn3 genes also can stimulate the expression of cBrn3c. We further found that Ath5 and Brn3 proteins are capable of transactivating a Brn3b promoter. Thus, these data suggest that the expression of cBrn3c in the chicken and Brn3b in the mouse is initially activated by Ath5 factors in newly generated ganglion cells and later maintained by a feedback loop of Brn3 factors in the differentiated ganglion cells.

Animals↗
PubMed2000

Caspase inhibitors block zinc-chelator induced death of retinal ganglion cells.

Zinc-chelating agents, including ethambutol and its metabolite 2,2'(ethylenediamino)-dibutyric acid (EDBA) are toxic to retinal ganglion cells through a glutamate dependent mechanism. We explored whether such cell death was mediated through the caspase family of cysteine proteases. Retinal cultures were treated with EDBA alone, or EDBA plus a variety of known caspase inhibitors, and ganglion cell viability was assayed. EDBA killed 20-30% of ganglion cells. A general caspase inhibitor, BAF, prevented EDBA induced ganglion cell death. Specific inhibitors of caspase-3 and caspase-6 showed a similar ability to BAF in preventing EDBA mediated ganglion cell loss, whereas inhibitors of caspase-8 and caspase-9 were not able to rescue EDBA treated ganglion cells. A caspase-1,4 inhibitor was less effective than BAF. These studies show that a caspase mediated mechanism of apoptosis accents for a portion of EDBA mediated retinal ganglion cell death. This toxicity was mediated by downstream effector caspases, 3 and 6. Caspase inhibitors may prevent ganglion cell death secondary to ethambutol treatment.

Animals↗
PubMed1991

Postmortem preservation of ganglion cells in the human retina. A morphometric investigation with the carbocyanine dye DiI.

Postmortem morphometric investigation of autopsy material is helpful for understanding the alterations cells undergo during life. The present work was undertaken to determine the morphologic features of human retinal ganglion cells during the first 2 days after death. Ganglion cells of 16 retinas were obtained from eyes, the corneas of which had been retrieved for keratoplasties. The ganglion cells were stained with the fluorescent carbocyanine dye Dil and investigated 12 to 36 hours postmortem. All labeled cells identified as ganglion cells had well preserved, type-specific dendritic profiles that made it possible to catalog them according to the established classes of ganglion cells. The various types of cells have in common some typical morphologic changes that occur during the postmortem period of observation: swelling and varicosity in the cell bodies and along the dendritic branches and the axons. These swellings were consistent throughout the postmortem period and did not hinder the identification of particular types of ganglion cells. The two major types (parasol and midget) and various subtypes of ganglion cells were identified morphologically. There are two distinct morphologic types of midget cells which differ from each other in the pattern of dendritic branching. Particular emphasis was given to analyze the dendritic geometry of the large parasol cells. A new finding in the human retina is the frequent presence of large parasol ganglion cells, the axons of which course along aberrant intraretinal paths, especially in the extreme periphery of the retina.

Axons↗
PubMed2005

Exogenous BDNF rescues rat spiral ganglion neurons in vivo.

OBJECTIVE: To determine if exogenous neurotrophins can prevent spiral ganglion neuron degeneration in the rat cochlea. BACKGROUND: The loss of hair cells resulting in sensorineural hearing loss also leads to the secondary degeneration of spiral ganglion neurons. The effectiveness of cochlear implantation in patients with profound sensorineural hearing loss relies in part on the survival of spiral ganglion neurons; therefore, any therapy that can prevent or halt the loss of these neurons would be of potential clinical benefit. Previous research has shown that intracochlear infusion with neurotrophins can provide trophic support to SGNs in deafened guinea pigs. Whether this effect is seen in other species remains to be determined. METHODS: After documenting the rate of spiral ganglion neuron degeneration after ototoxic deafening, we investigated the trophic effects of exogenous brain-derived neurotrophic factor (BDNF) on rat spiral ganglion neurons. The left cochleae of profoundly deafened rats were implanted with a drug delivery system connected to a mini-osmotic pump. BDNF or artificial perilymph was infused for 28 days; then the cochleae were prepared for histological study. RESULTS: Treatment with BDNF led to a statistically significant increase in spiral ganglion neuron density and a highly significant increase in spiral ganglion neuron soma area compared with artificial perilymph-treated and untreated deafened cochleae. CONCLUSION: The study has demonstrated the trophic advantage of exogenous BDNF in the mature rat cochlea and provides confidence that spiral ganglion neuron rescue after sensorineural hearing loss with exogenous BDNF may have clinical application.

Animals↗
PubMed2007

The radiographic prevalence of geniculate ganglion dehiscence in normal and congenitally thin temporal bones.

OBJECTIVE: To determine the prevalence of a dehiscent geniculate ganglion on routine temporal bone computed tomography (CT). STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Two hundred seventy-eight consecutive temporal bone CT examinations for a total of 556 sides were reviewed. One hundred ninety-one sides were excluded. Reasons for exclusion included reconstructed coronal views, no coronal views, or a pathologic process, which involved the geniculate ganglion. Six examinations were from patients with clinical superior canal dehiscence confirmed by surgical repair or positive vestibular evoked myogenic potentials. Twenty-four scans were from patients with radiographic superior canal dehiscence confirmed by two independent readings. MAIN OUTCOME MEASURES: The incidence of geniculate ganglion dehiscence in patients with and without radiographic or clinical superior canal dehiscence. Dehiscent geniculate ganglion was defined as at least two consecutive cuts on a coronal CT showing no bone overlying the geniculate ganglion. RESULTS: The overall incidence of a dehiscent geniculate ganglion was 14.5% in the 365 sides reviewed. The incidence of a dehiscent geniculate ganglion is increased in patients with radiographic and clinical superior canal dehiscence as compared with normal patients and was significantly different by chi analysis (38.1 versus 11.4%). CONCLUSION: The presence of radiographic geniculate ganglion dehiscence is common. This finding has particular importance when the middle cranial fossa or subtemporal approach is used, as the facial nerve is more at risk especially when used to address superior canal dehiscence.

Adolescent↗
PubMed2005

Synaptic contacts between an identified type of ON cone bipolar cell and ganglion cells in the mouse retina.

We surveyed the potential contacts between an identified type of bipolar cell and retinal ganglion cells in the mouse. By crossing two existing mouse strains (line 357 and line GFP-M), we created a double transgenic strain in which GFP is expressed by all members of a single type of ON cone bipolar cell and a sparse, mixed population of retinal ganglion cells. The GFP-expressing bipolar cells appear to be those termed CB4a of Pignatelli & Strettoi [(2004) J. Comp. Neurol., 476, 254-266] and type 7 of Ghosh et al. [(2004) J. Comp. Neurol., 469, 70-82 and J. Comp. Neurol., 476, 202-203]. The labelled ganglion cells include examples of most or all types of ganglion cells present in the mouse. By studying the juxtaposition of their processes in three dimensions, we could learn which ganglion cell types are potential synaptic targets of the line 357 bipolar cell. Of 12 ganglion cell types observed, 10 types could be definitively ruled out as major synaptic targets of the line 357 bipolar cells. One type of monostratified ganglion cell and one bistratified cell tightly cofasciculate with axon terminals of the line 357 bipolar cells. Double labelling for kinesin II demonstrates colocalization of bipolar cell ribbons at the sites of contact between these two types of ganglion cell and the line 357 bipolar cells.

Animals↗
PubMed2005

Lens injury stimulates adult mouse retinal ganglion cell axon regeneration via both macrophage- and lens-derived factors.

In the present study the effects of lens injury on retinal ganglion cell axon/neurite re-growth were investigated in adult mice. In vivo, lens injury promoted successful regeneration of retinal ganglion cell axons past the optic nerve lesion site, concomitant with the invasion of macrophages into the eye and the presence of activated retinal astrocytes/Muller cells. In vitro, retinal ganglion cells from lens-lesioned mice grew significantly longer neurites than those from intact mice, which correlated with the presence of enhanced numbers of activated retinal astrocytes/Muller cells. Co-culture of retinal ganglion cells from intact mice with macrophage-rich lesioned lens/vitreous body led to increased neurite lengths compared with co-culture with macrophage-free intact lens/vitreous body, pointing to a neurotrophic effect of macrophages. Furthermore, retinal ganglion cells from mice that had no lens injury but had received intravitreal Zymosan injections to stimulate macrophage invasion into the eye grew significantly longer neurites compared with controls, as did retinal ganglion cells from intact mice co-cultured with macrophage-rich vitreous body from Zymosan-treated mice. The intact lens, but not the intact vitreous body, exerted a neurotrophic effect on retinal ganglion cell neurite outgrowth, suggesting that lens-derived neurotrophic factor(s) conspire with those derived from macrophages in lens injury-stimulated axon regeneration. Together, these results show that lens injury promotes retinal ganglion cell axon regeneration/neurite outgrowth in adult mice, an observation with important implications for axon regeneration studies in transgenic mouse models.

Animals↗
PubMed1974

Effect of preganglionic nerve stimulation on sensitivity of the superior cervical ganglion to nicotinic blocking agents.

1 Periodic stimulation (every 10 min) of the cervical sympathetic nerve increased the ganglionic block by low concentrations of chlorisondamine (CHL) in the superior cervical ganglion of the cat when compared to the contralateral unstimulated side.2 Periodic stimulation of the postganglionic nerve was ineffective in increasing the block.3 Ganglionic block by low concentrations of mecamylamine had the same stimulus dependency, but ganglionic block by any dose of hexamethonium was not influenced by nerve stimulation.4 Physostigmine infused together with CHL increased the rate of onset of block produced by CHL. Atropine had no apparent effect on the development of ganglionic block by CHL.5 Repeated intra-arterial injections of 1,1-dimethyl-4-phenylpiperazinium into the circulation of the superior cervical ganglion increased the magnitude of block produced by CHL. Similar injections of methacholine had no effect on ganglionic block produced by CHL.6 The results are interpreted to indicate that activation of ganglionic nicotinic receptors increased the affinity of receptors for CHL and mecamylamine.

Animals↗
PubMed1982

Intracellular recordings from the stellate ganglion of the cat.

1. Intracellular recordings were made, in vitro, and in situ, from neurones of the cat stellate ganglion. 2. Preganglionic stimulation, in vitro, via the T3 ramus or post-ganglionic stimulation via the ventral ansa, dorsal ansa or stellate cardiac nerve evoked graded synaptic responses which led to the discharge of one or more action potentials. Since the conduction velocities of fibres converging onto a single cell may vary, their convergence may mean that there is an interaction in the stellate ganglion between functionally different pathways. 3. Most neurones in the stellate ganglion receive synaptic input from fibres of both central and peripheral origin. 4. Intracellular recordings were made, in situ, from neurones of the cat stellate ganglion attached via the stellate cardiac nerve to the rest of the animal. When peripheral sympathetic afferent input to the stellate ganglion was increased by occluding the descending aorta, some of the neurones exhibited an increase in excitatory post-synaptic potentials (e.p.s.p.s) and/or action potentials. Most of the synaptic input recorded from the ganglion cells in situ had a close relationship with the cardiac cycle and/or respiration. 5. These data and our previous studies support the contention that sympathetic efferent nerve activity can be modified by peripheral excitatory inputs and that these neural connexions may function as pathways for a peripheral reflex at the level of the paravertebral ganglion.

Action Potentials↗