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PubMed1989

Effects of alpha adrenoceptor and dopamine receptor agonists and antagonists on ganglionic transmission.

Effects of alpha adrenoceptor and dopamine (DA) receptor agonists and antagonists on ganglionic transmission were studied in pentobarbital-anesthetized, open-chest dogs. Changes in tachycardia produced by preganglionic cardiac nerve stimulation were monitored as a measure of ganglionic transmission. Several agonists, injected i.a. into the blood supply of the stellate ganglion, inhibited ganglion transmission. This effect was localized to the ganglion as none of the agonists, in the highest doses studied, inhibited tachycardia produced by postganglionic cardiac nerve stimulation. The potency order of the agonists was UK 14,304 (alpha-2 adrenoceptor agonist) greater than norepinephrine (NE) greater than dipropyl DA (DA2 dopamine receptor agonist) greater than DA greater than or equal to phenylephrine (alpha-1 adrenoceptor agonist) greater than fenoldopam (DA1 dopamine receptor agonist). UK 14,304 was over 200 times more potent than fenoldopam, being active in nanomole doses, whereas NE was more potent than DA. Rauwolscine, an alpha-2 adrenoceptor antagonist, antagonized the inhibitory effects of NE and DA and was the only antagonist, given i.a. or i.v., that facilitated ganglionic transmission; frequency-response curves of tachycardia induced by preganglionic nerve stimulation were dose-dependently augmented. SCH 23390, in double the full DA1 antagonist dose, had no effect on frequency-response curves or on NE- or DA-induced ganglionic inhibition. Domperidone antagonized the effect of DA but had no effect on ganglionic inhibition produced by NE or on frequency-response curves of tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Agonists↗
PubMed1986

Topography of NPY-, somatostatin-, and VIP-immunoreactive, neuronal subpopulations in the guinea pig celiac-superior mesenteric ganglion and their projection to the pylorus.

The topography of the peptidergic neuronal subpopulations in the guinea pig celiac-superior mesenteric ganglion was studied analyzing the distribution of immunoreactivity to neuropeptide Y (NPY), somatostatin (SOM), and vasoactive intestinal polypeptide (VIP)/polypeptide HI (PHI). For comparison, the ganglion was also studied using antisera against the 2 catecholamine-synthesizing enzymes tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH). Approximately 65% of the neuronal cell bodies contained NPY-like immunoreactivity (NPY-LI), whereas 25% of the principal ganglion cells contained SOM-like immunoreactivity (SOM-LI). Though occasional cells were found to contain both NPY-LI and SOM-LI, these peptides had a complementary distribution in the ganglion, with NPY cells in the celiac poles and SOM cells in the superior mesenteric pole. The vast majority of both the NPY- and SOM-positive cells also contained TH-like immunoreactivity (TH-LI), confirming their catecholaminergic, presumably noradrenergic, nature. Some noradrenergic neurons seemed to lack NPY- and SOM-LI. Small numbers of VIP/PHI-containing cell bodies were found in areas where the NPY-immunoreactive neurons predominated. Many of the VIP/PHI-positive cells contained NPY-LI and occasionally also TH-LI. The immunohistochemical markers were also observed in fibers. Thus, a comparatively weak NPY-LI was seen in smooth fibers, probably representing axons and axon bundles. SOM-LI was seen in a similar type of fiber but also in more strongly fluorescent fibers with a varicose appearance. The latter fibers were observed only in the SOM-dominated part of the ganglion, often surrounding the ganglion cells. Varicose fibers with a similar distribution containing DBH-like immunoreactivity (DBH-LI) were also seen. In addition, DBH- and TH-LI were seen in smooth axonlike processes. VIP-positive fibers exhibited a very dense fiber network, almost exclusively related to the SOM cell-dominated part of the ganglion. The projection of the postganglionic sympathetic neurons was studied with special reference to the pylorus using a combination of retrograde axonal tracing and indirect immunofluorescence techniques. Seventy-two hours after injection of the fluorescent tracer Fast Blue into the pyloric sphincter, labeled neurons were found in the ganglion. By comparing the Fast Blue-labeled cells with the immunoreactive cell bodies, neurons containing both dye and NPY- or SOM-LI were observed. In elution-restaining experiments, it was established that the majority of these cells were also immunoreactive to TH, indicating that they produce noradrenaline.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Morphological changes in the vestibular epithelia and ganglion induced by ototoxic drug.

The morphological changes of the vestibular sensory epithelia and the vestibular ganglions induced by Gentamicin(GM) were investigated using scanning electron microscope, transmission electron microscope and light microscope. The guinea pigs were injected with a single application of 4 mg (0.1ml) of GM into the middle ear through the tympanic membrane. The vestibular organs and the ganglions were observed up to 6 months after the treatment. Four days after the injection, fused, ballooned and missing cilia were observed in the vestibular sensory epithelia. These changes progressed and extended toward the periphery of the crista and the macula. The changes of the vestibular ganglions were first observed one month after the treatment. The degenerative process started from destruction of the mitochondrial cristae and vacuolization of the cytoplasm in the Schwann cell. The next step of the change was dissociation of the myelin sheath around the ganglion cell. The cytoplasmic organelles in the ganglion cell gradually deteriorated. At the later stage, the myelin sheath around the ganglion cell disappeared and the number of the cell reduced. Furthermore, the myelin sheath of the nerve fiber was dissociated. In this study the signs of the vestibular ganglion damage were later than that of the vestibular organ. However, we thought the changes in the ganglion are probably due to direct influence of GM, since the degeneration was found to develop in a relatively short period.

Acoustic Maculae↗
PubMed1987

Growth and morphogenesis of an autonomic ganglion. II. Establishment of neuron position.

The developmental events affecting the positioning of neurons were examined in the frog cardiac ganglion. Use of a neuron-specific marker enabled the position of all neurons in the ganglion to be quantified at different developmental stages. Subsets of neurons born at specific times were labeled with 3H-thymidine, and their positions were mapped at different developmental stages. This technique identifies a subset of cells within a seemingly homogeneous pool of neurons and provides an opportunity for studying the position of individual neurons during ganglion morphogenesis. Comparison of identified neurons in different animals has revealed several unexpected results. First, during a period of dramatic ganglion and cellular morphogenesis there is little or no cell death since the number of identified neurons does not change during this time. Second, the distinctive clusters that are characteristic of parasympathetic ganglia have been shown to be ephemeral because identified cells that were neighbors early in development become separated during ganglion morphogenesis. Third, individual postmitotic neurons do not actively migrate to produce the observed changes in neuron distribution, as evidenced by the fact that their relative position in the ganglion is maintained. Fourth, both ganglion and target undergo intercalary growth since the absolute distance of identified neurons from one another increases while the relative distance remains the same. Finally, the differentiation of neurons is analogous to the inside-out pattern seen in many parts of the CNS. Thus the ability to identify cells within a large ensemble of seemingly equivalent neurons has made it possible to investigate ganglion morphogenesis at the level of individual cells.

Acetylcholinesterase↗
PubMed1979

Synaptic drive and impulse generation in ganglion cells of turtle retina.

1. Light reponses and electrical constants of ganglion cells in the retina of the turtle were examined by intracellular recording in eyecup preparations. 2. In 'on', 'off', and 'on/off' cells, the impulses produced by illumination of the centre of the receptive field arose from slow synaptic depolarizations. The ganglion cells also exhibited inhibitory synaptic potentials. 3. The synaptic depolarization evoked by a step change in light intensity rose more slowly than the response of the cones in which the excitation originated, and the depolarization then declined in spite of a well maintained cone response. This behaviour is consistent with the notion advanced previously that, during transmission to ganglion cells, receptor signals are relayed through the equivalent of a bandpass filter. 4. The e.p.s.p.s evoked by light grew when the membrane was hyperpolarized by injected current and decreased when the membrane was depolarized. The i.p.s.p.s reversed at a level slightly negative to the resting potential in darkness. 5. In neither 'on' nor 'off' ganglion cells did the synaptic potentials evoked by step changes in illumination show the hyperpolarizing phases expected of a linear filter. The absence of hyperpolarizations is consistent with a rectification which permits transmission of depolarizations but not hyperpolarizations from bipolar to ganglion cells. 6. In darkness the membrane potential of some ganglion cells showed random depolarizations which brought the potential near the threshold for impulse generation. 7. With very small spots in the receptive field centre the 'on' responses of ganglion cells to flashes and steps of light grew approximately linearly with stimulus intensity. The step reponse was not, however, related to the flash response by superposition. Larger spots in the field centre gave responses which grew non-linearly with the intensity of even dim stimuli. 8 Depolarizing current passed through the recording electrode elicited a repetitive discharge of impulses. The frequency of firing increased linearly with current strength above a rheobase value of about 10(-10) A. Accommodation occurred during steady currents, the main decline taking place with a time constant of about 15 msec. 9. Strength-latency measurements and bridge records of ganglion cell charging by constant currents gave time constants of 10--20 msec and input resistances of 100--150 M omega.

Action Potentials↗
PubMed1983

Muscarinic receptor binding and oxidative enzyme activities in the adult rat superior cervical ganglion: effects of 6-hydroxydopamine and nerve growth factor.

Administration of 6-hydroxydopamine to adult rats results in changes in the superior cervical ganglion similar to those noted after axotomy; namely, a decrease in muscarinic receptor binding and increases in activities of the oxidative enzymes of the pentose phosphate pathway. These changes were either prevented or attenuated markedly by the systemic administration of nerve growth factor. Administration of nerve growth factor alone did not significantly increase N-methylscopolamine binding in the ganglion or reduce the activities of the oxidative enzymes. Explants of the ganglion maintained in serum-free medium over a period of 3 days demonstrated increases in oxidative enzyme activity and a decrease in N-methylscopolamine binding. Addition of 20 nM nerve growth factor to the culture medium prevented the decline in N-methylscopolamine binding in ganglion explants. The increases in oxidative enzyme activities were unaltered. Addition of high amounts of nerve growth factor, 200 nM, resulted in a significant increase in tyrosine hydroxylase activity but no further increase in N-methylscopolamine binding in ganglion explants. Glucocorticoids added to the culture medium did not affect the muscarinic binding or enzyme activities. Thus, decreases in muscarinic binding activity which occur in the superior cervical ganglion after axotomy or 6-hydroxydopamine treatment may be explained by a loss of nerve growth factor supplied to the ganglion. Increases in the oxidative enzymes of the pentose phosphate pathway that occur in the ganglion after axonal injury appear to involve additional factors.

Animals↗
PubMed1976

[Electrophysiologic study of propagation of excitation in the cat pterygopalatine ganglion].

Action potentials were studied in nerves of the cat pterygopalatine ganglion evoked by stimuli applied to other nerves of the ganglion (in situ). It is established that most fibres passing through the ganglion are continuous sympathetic postganglionic fibres (not less than 3 groups). Most parasympathetic preganglionic fibres are synaptical on the ganglionic neurons and are represented by a group of fibres with the same threshold of excitation. Intracellular recording from single neurons of the pterygopalatine ganglion showed that stimulation of the Vidian nerve caused orthodromic spikes with short latency in one group of neurons and spikes with long latency in other neurons (2.5-6 ms and 10-40 ms respectively). Only fast fibres appear to terminate on most neurons of the ganglion, and only slow fibres do on some other neurons. Tonic activity was not observed when was performed from intact nerves of the pterygopalatine ganglion. The interacellular recording from single neurons of the ganglion showed that frequency of spike potentials either is low (1-3 per second) in some neurons or the potentials are absent in general in other neurons.

Animals↗
PubMed1990

Basic fibroblast growth factor: receptor-mediated internalization, metabolism, and anterograde axonal transport in retinal ganglion cells.

Basic fibroblast growth factor (bFGF) was radiolabeled and used in axonal transport studies to determine whether certain neuronal populations express functional receptors for bFGF. Unlike 125I-NGF, 125I-bFGF was not retrogradely transported in the adult rat sciatic nerve or from iris to trigeminal ganglion or superior cervical ganglion. However, after intraocular injection of 125I-bFGF into the posterior chamber of the eye of adult rats, radioactivity was detected within the retinal ganglion cell projections. This radioactivity was localized to the ipsilateral optic nerve and in the contralateral lateral geniculate body and the contralateral superior colliculus by using autoradiographic techniques. Direct measurement of the radioactivity in dissected brain regions was used to study the process of 125I-bFGF uptake and transport by retinal ganglion cells. The uptake and transport were specific for biologically active bFGF since neither denatured, biologically inactive 125I-bFGF nor 125I-NGF was taken up and transported. The uptake and transport of 125I-bFGF were saturable phenomena since they were blocked in the presence of excess, unlabeled bFGF. Wheat germ agglutinin, but not heparinase, blocked uptake and transport of 125I-bFGF, a finding that is consistent with the uptake being mediated by high-affinity bFGF receptors. Radioactivity from 125I-bFGF was transported in retinal ganglion cell axons in an anterograde direction at a maximum rate in excess of 1.7 mm/hr. No specific retrograde transport of bFGF to the retina was detected after 125I-bFGF was injected into the superior colliculus. The radioactivity from 125I-bFGF that accumulated in the superior colliculus was lost from this tissue with a half-life of about 22 hr. Autoradiography of proteins separated by SDS-PAGE demonstrated that 125I-bFGF was not substantially degraded in the retina after internalization within retinal ganglion cells. During anterograde transport, however, 125I-bFGF underwent limited proteolytic cleavage resulting in 3 prominent 125I-bFGF derivatives of molecular weights greater than 7000 Da. Although these were the major radioactive species recovered from the superior colliculus after intraocular injection, some intact 125I-bFGF was also detected within the innervated target. These results indicate that retinal ganglion cells express high-affinity receptors for bFGF, that these receptors mediate the internalization of bFGF, that internalized bFGF undergoes limited proteolytic cleavage, and that bFGF and its derivatives are anterogradely transported to the lateral geniculate body and the superior colliculus. These data raise the possibility that bFGF or its derivatives may act as an anterograde trophic factor in the visual system, a system that is known to undergo anterograde transneuronal cell death.

Animals↗
PubMed1992

Morphometric analysis of macular photoreceptors and ganglion cells in retinas with retinitis pigmentosa.

There have been a number of histopathologic studies of retinas that were taken post mortem from patients with retinitis pigmentosa (RP), but few have addressed the question of transneuronal degeneration of ganglion cells secondary to photoreceptor death. We studied sectioned maculae that were obtained from 41 patients with different genetic forms of RP: autosomal dominant (n = 11); X-linked (n = 9); and simplex (n = 21). We also studied sectioned maculae that were taken from 20 age-matched normal subjects. We counted cell bodies in the photoreceptor and ganglion cell layers at 100-microns (0.35 degrees) intervals from the foveola to 1500-microns eccentricity and compared the mean cell counts among each group with RP. Each RP type had significantly fewer (P < .05) photoreceptors than those of the control group at each 100-microns interval. At eccentricities of 700 to 1500 microns, the retinas with X-linked and autosomal dominant RP had significantly fewer (P < .05) ganglion cells than those of the control group; the simplex RP mean ganglion cell counts were significantly lower (P < .05) than those of the control group, from 1000 to 1500 microns. The mean photoreceptor and ganglion cell counts had a .43 correlation (P < .001) in the zone of 700 to 1500 microns, consistent with transneuronal ganglion cell degeneration. Current experimental attempts to restore vision in diseased retinas by simulating or replacing photoreceptors are based on the premise that ganglion cells are retained after photoreceptor death. Our findings support this assumption.

Adolescent↗
PubMed1997

Tracer coupling pattern of amacrine and ganglion cells in the rabbit retina.

We examined the tracer coupling pattern of more than 15 morphological types of amacrine and ganglion cells in the rabbit retina. Individual cells were injected intracellularly with the biotinylated tracer Neurobiotin, which was then allowed to diffuse across gap junctions to label neighboring neurons. We found that homologous and/or heterologous tracer coupling was common for most proximal neurons. In fact, the starburst amacrine cell was the only amacrine cell type that showed no evidence of coupling. The remaining types of amacrine cell were coupled exclusively to other amacrines, either homologously or, more often, through a combination of homologous and heterologous junctions. In only one case did we visualize labeled ganglion cells following injection of Neurobiotin into an amacrine cell. In contrast, injection of Neurobiotin into ganglion cells almost always resulted in the labeling of amacrine cells. Taken together, these results suggest a directionality to the movement of tracer across gap junctions connecting amacrine and ganglion cells. We found that the coupling pattern for a given morphological type of cell was generally stereotypic and consistent across retinas. The notable exceptions to this finding were alpha ganglion cells and cells with morphology corresponding to that of on-off direction selective ganglion cells. In both cases, individual cells showed either extensive coupling to both amacrine and ganglion cells or no coupling at all. A notable finding was that, in every case, the neighboring cells within a tracer-coupled array were always within one gap junction of the injected neuron. Furthermore, in many cases, the array formed by the somata of tracer-coupled cells was almost perfectly coincident with the dendritic arbor of the injected cell. Thus, our results indicate that whereas coupling is extensive within the proximal retina, individual cells partake in coupled networks that are stereotypic and highly circumscribed.

Animals↗
PubMed1983

Developmental relationships between trigeminal ganglia and trigeminal motoneurons in chick embryos. II. Ganglion axon ingrowth guides motoneuron migration.

In the chick embryo the trigeminal (V) sensory ganglion cells send axons into the metencephalon a few hours before the V motoneurons migrate from the midline to form a lateral nucleus adjacent to the ingrowing sensory axons. This relationship suggests that the ganglion axons may influence the initiation and direction of V motoneuron migration. In the present experiment the development of the ganglion axons was retarded by removing the neural crest anlage of the V ganglion. Subsequently, V ganglion cells which were derived from the ectodermal placode anlage sent axons into the metencephalon up to 2 days later than normal. The lateral migration of the V motoneurons was similarly delayed, commencing only after the central axons from the placodal ganglia penetrated the metencephalon. This study demonstrates that the presence of V ganglion perikarya alone is not sufficient to guide the appropriate migration of V motoneurons. This migration occurs only after the axons from the V sensory ganglion cells have penetrated the brainstem.

Animals↗
PubMed1986

Retinal crowding alters the morphology of alpha ganglion cells.

It has been hypothesized that the dendritic field size of individual retinal ganglion cells is regulated early in development by interactions among neighboring cells (Wässle and Reiman, Proc. R. Soc. Lond. B. 200:441-461, 1978). An opportunity to test this hypothesis is provided by the consequences of prenatal enucleation that results in an increased density of ganglion cells in the remaining retina (Chalupa et al., Neuroscience 12:1139-1146, 1984). In the present study we compared dendritic field diameters of alpha ganglion cells in normal retinas to those of adult cats that were monocularly enucleated before birth (on embryonic days 42 and 51) and 6 days after birth. In each animal ganglion cells were labeled by central injections of horseradish peroxidase. The retinas were incubated according to a modified Hanker-Yates procedure and whole-mounted. All cells were sampled from the temporal retina along a corridor established by a line drawn through the optic disk and the area centralis. Alpha cells were differentiated into ON and OFF subtypes on the basis of their level of stratification in the inner plexiform layer (Peichl and Wässle, Proc. R. Soc. Lond. B. 212:139-156, 1981). Dendritic field and soma diameters were determined from complete cell drawings by calculating the mean of the two longest orthogonal diameters. Our main findings are: Early monocular enucleation does not disrupt the mosaics of ON and OFF alpha ganglion cells in the remaining retina of adult animals. Within the retinal corridor sampled, the density of alpha cells was substantially greater than normal in the remaining retina of the prenatal enucleates at all eccentricities except the far periphery. Except at the far periphery, the dendritic field diameters of the prenatally enucleated animals were significantly smaller than normal when compared at equivalent eccentricities. However, when compared at equivalent cell densities, dendritic field dimensions in the prenatally enucleated and normal animals were found to be similar. In the prenatal enucleates the somas of these neurons were also significantly smaller than normal. If the monocular enucleation was postnatal, however, the density and the dendritic field diameters of alpha cells did not differ appreciably from normal. These results indicate that the morphology of retinal ganglion cells can be influenced by increasing the density of developing ganglion cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Morphology and distribution of neurons in the retinal ganglion cell layer of the adult tammar wallaby--Macropus eugenii.

The morphology of the ganglion cell layer of the adult tammar wallaby has been examined from Nissl-stained retinal flatmounts. From this material, neurons have been classed as ganglion cells or displaced amacrine cells according to the disposition of Nissl substance. A further subdivision of ganglion cells into a separate group of alphalike cells was assisted by determining the range of soma sizes in neurofibrillar-stained flatmounts, a method which, in the cat, has revealed the presence of alpha cells. Isodensity contour maps prepared from the Nissl-stained flatmounts show a well-developed visual streak and an area centralis in the total neuronal population. A similar pattern was also found in the ganglion cells, thus confirming Tancred's (J. Comp. Neurol. 196:585-603, '81) finding, and, as well, in the alphalike ganglion cells and the displaced amacrine cells. The relative proportions of ganglion cells to displaced amacrines (GC:DA) were evaluated from isodensity profiles drawn along and vertical to the visual streak for the two cell types and also from maps showing the variation in the GC:DA ratio throughout the retina. A comparison with results published for other species shows that the visual streak development in the tammar wallaby is consistent with the expectations of the "terrain" theory and that, in its relative proportion of displaced amacrines, the tammar closely resembles the rabbit but contrasts sharply with the cat, which has half as many ganglion cells and three times as many displaced amacrines as the other two species.

Animals↗
PubMed1987

Role of cell death in the topogenesis of neuronal distributions in the developing cat retinal ganglion cell layer.

The neurons of the developing and adult ganglion cell layer of the cat retina may be morphologically divided into two major populations. One population, the classic neurons, is mainly composed of ganglion cells, and of a small percentage of displaced amacrines, the bar cells. The remaining neurons are microneurons, which make up the majority of the displaced amacrine population. The loss of ganglion cells during the development has been attributed to cell death. It has alternatively been suggested that some ganglion cells may lose their axon and be transformed into displaced amacrine cells, without degeneration of the cell soma. Reexamination of foetal and postnatal cat retinas confirms the presence of degenerating cells in the ganglion cell layer. Their number appears to be at a maximum on embryonic day (E) 57 but declines rapidly until birth. The peak of cell death thus coincides with the decline in optic nerve fibre counts and classical neuron or ganglion cell numbers. Some cells in early stages of degeneration resemble classical neurons, but the original morphology of those advanced stages of degeneration could not be identified, nor was it possible to identify pyknotic microneurons at any stage. Substantial degeneration of the microneurons is not suggested but if it occurs, it is masked by an overall increase in the population of these cells before birth. Cell death in the microneuron population thus cannot yet be ruled out. It has been argued in the literature that fragments of degenerating cells in developing neural tissue are cleared by microglia within 10-14 hours. In order to test the hypothesis that operation of cell death can alone account for the observed loss of classical neurons in the foetal cat retina, we have modelled the effect of various presumed clearance times on corresponding neuronal population magnitudes. It is found that a constant clearance time of 10-24 hours would be consistent with the observed loss of classical neurons before birth. If this is true, then no ganglion cells would remain for transformation into amacrine cells. The absolute density of degenerating or pyknotic cells is found to be relatively constant across the retina. However their density expressed as a percentage of the local population of classical neurons is markedly higher in peripheral than central retina. In the former region, they compose more than 10% of classical neurons at stage E57. On the same day, the percentage distribution maps define an elongated central area containing only 3-5% pyknotic profiles. This region corresponds to the location of the future visual streak.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Distribution of substance P-like immunoreactive retinal ganglion cells and their pattern of termination in the optic tectum of chick (Gallus gallus).

Substance P-like immunoreactive (SP-LI) neurons were identified within the inner nuclear layer and ganglion cell layer of the chick retina. The SP-LI cells in the inner nuclear layer consisted of several subtypes of neurons, differing in soma size and dendritic arborization. In the ganglion cell layer a population of moderately labelled SP-LI neurons was also present. About 6-9 microns in diameter and spaced 50-80 microns apart, they formed a regular array across the entire retina, with a density of about 400 cells/mm2 in the superior temporal retina, declining to less than 100 cells/mm2 in the peripheral retina. The total number of SP-LI cells in the ganglion cell layer was approximately 75,000. Individual axons could be followed toward the optic nerve head. Lesions near the optic nerve head resulted in axotomy of ganglion cells within a limited portion of the retina. Two days of postaxotomy there were numerous SP-LI swellings in the proximal segments of axotomized axons. SP-LI neurons in the axotomized zone were larger, more numerous, and showed increased staining of their processes. Fourteen days following a retinal lesion, there was depletion of all SP-LI cells in the ganglion cell layer within the axotomized zone, but the SP-LI neurons in the inner nuclear layer were not noticeably affected. Following a localized injection of rhodamine-coupled latex beads into the optic tectum, a population of retinal ganglion cells (RGCs) in the contralateral retina was retrogradely labelled. Many of these cells also exhibited SP-like immunoreactivity. Examination of the optic tectum indicated the presence of SP-LI fibres in laminae 2-13 (nomenclature of Cajal: Histologie du Systeme Nerveux. Vol. 2. Paris: Maloine, '11), with immunoreactive terminal regions present mainly in laminae 2-4, 7, and 9-13. SP-LI cell bodies were found predominantly in laminae 10-12 and 13. Fourteen days following a retinal lesion, SP-LI processes and terminals were depleted from laminae 2 and 3. Immunoreactive cells and processes in the remaining laminae of the optic tectum were not noticeably altered. The present report confirms the existence of SP-LI retinal ganglion cells in the chick retina and demonstrates their contribution to lamina specific SP-LI arborization in the optic tectum.

Animals↗
PubMed1988

Anatomical consequences of neonatal infraorbital nerve transection upon the trigeminal ganglion and vibrissa follicle nerves in the adult rat.

A large body of experimental literature has demonstrated that neonatal infraorbital nerve damage in rodents produces anatomical and/or functional alterations of the normal whisker representation in central trigeminal structures. Less is known about the organization of primary afferent components of the trigeminal system following this manipulation. Such information provides an important basis for interpreting the central changes observed following damage of infraorbital nerve fibers at birth. We have therefore examined the composition and order of peripheral innervation in the pathway from the trigeminal ganglion to the vibrissa follicles in adult rats subjected to unilateral neonatal infraorbital nerve transection. Electron microscopy was used to determine the number and diameter of myelinated and unmyelinated fibers in vibrissa follicle nerves of these animals. Wheat germ agglutinin-horseradish peroxidase and fluorescent retrograde tracers were employed to examine the number and diameter, as well as the topographic organization and branching, of ganglion cells innervating the vibrissae in these rats. The data presented below indicate that neonatal infraorbital nerve transection has the following consequences within the adult trigeminal nerve and ganglion: 1) an alteration of the gross morphology of vibrissal nerves, 2) a significant reduction in the average number (85.4%) and diameter (32.6%) of myelinated, but not unmyelinated, follicle nerve axons, 3) a significant decrease in the average number (36.8%) of trigeminal ganglion cells innervating vibrissa follicles, 4) no significant change in the distribution of ganglion cell diameters, 5) an increase in peripheral branching (1.8-fold) of these ganglion cell axons, and 6) an alteration of somatotopic order within the trigeminal ganglion. Taken together, these data indicate that neonatal infraorbital nerve transection produces a profound reorganization of the primary afferent component of the trigeminal neuraxis.

Animals↗
PubMed1989

Fetal brain grafts rescue adult retinal ganglion cells from axotomy-induced cell death.

After intraorbital transection of the optic nerve of adult rats, 90% of the retinal ganglion cells die within 30 days. Since fetal brain extracts and cocultured fetal target regions support the survival of retinal ganglion cells in vitro (Nurcombe and Bennett: Exp. Brain Res. 44: 249-258, '81; McCaffery et al.: Exp. Brain Res. 48: 377-386, '82; Armson and Bennett: Neurosci. Lett. 38: 181-186, '83) we investigated whether cell death in the adult retina could be prevented by transplanting fetal (E16) thalamus and tectum to the proximal stump of the optic nerve of adult rats that was completely transected 2-3 mm behind the optic disc. Unoperated eyes contained 119,973 (+/- 939, SEM) retinal ganglion cells, estimated from axon counts of the intact optic nerve. Of these, 11,601 (+/- 1,857) remained in control operated eyes at 30 days postoperation while in the eyes of grafted rats, 35,086 (+/- 2,278) retinal ganglion cells were counted. Thus, 23,485 (= 22% of those normally dying after transection of the optic nerve) ganglion cells were rescued by the fetal grafts from cell death normally following axotomy. These results indicate that fetal target regions of retinal ganglion cells contain and/or produce neurotrophic molecules that promote the survival of adult axotomized retinal ganglion cells.

Animals↗
PubMed1989

Topographic organization of the central projections of the spiral ganglion in cats.

The morphological organization of inputs from restricted sectors of the cat cochlear spiral ganglion into the cochlear nucleus was studied by making focal extracellular injections of horseradish peroxidase (HRP) into the spiral ganglion. Injections resulted in Golgi-like labeling of a small cluster of spiral ganglion cells and their peripheral and central axons. Large injections involved most of the cells within Rosenthal's canal in sectors of the spiral ganglion innervating greater than or equal to 1 mm of the basilar membrane and resulted in narrow, complete laminae of labeled axons and preterminal fields within each cochlear nucleus subdivision. The positions of these bands were consistent with the "isofrequency laminae" appropriate for the frequencies represented at the injection sites, with high frequency laminae situated more dorsally, and lower frequencies progressively more ventral. A discrete projection to the small cell cap area was observed that was discontinuous with the main projection laminae in the ventral cochlear nuclei (VCN). In the dorsal cochlear nucleus, projecting fibers and terminals were excluded from the molecular cell layer. No labeled fibers entered the granule cell areas. In contrast to larger injections, very small HRP deposits labeled only part of an isofrequency lamina. Specifically, injections restricted to the scala tympani aspect of the spiral ganglion labeled only the lateral part of VCN isofrequency laminae, whereas injections limited to the scala vestibuli aspect of the ganglion labeled the medial aspect of the isofrequency planes. Thus these data indicate a previously unrecognized topographic representation of the vertical dimension of the spiral ganglion across VCN isofrequency laminae. Some possible functional implications of this projection organization are discussed.

Animals↗