Element Distribution in Visual System,the Optic Chiasma,Lateral Geniculate Body,and Superior Colliculus

To elucidate compositional changes of the visual system with aging, the authors investigated age-related changes of elements in the optic chiasma, lateral geniculate body, and superior colliculus, relationships among their elements, relationships among their brain regions from a viewpoint of elements, and gender differences in their elements by direct chemical analysis. After ordinary dissection at Nara Medical University was finished, the optic chiasmas, lateral geniculate bodies, and superior colliculi were resected from identical cerebra of the subjects. The subjects consisted of 14 men and 10 women, ranging in age from 75 to 96 years (average age = 85.6 ± 5.9 years). After ashing with nitric acid and perchloric acid, element contents were determined by inductively coupled plasma-atomic emission spectrometry. As the result, the average content of P was significantly higher in the optic chiasma and superior colliculus compared with the lateral geniculate body. Regarding age-related changes of elements, no significant changes with aging were found in seven elements of the optic chiasma, lateral geniculate body, and superior colliculus in the subjects more than 75 years of age. The findings that with regard to the relationships among elements, there were extremely significant direct correlations between Ca and Zn contents and significant inverse correlations between Mg and Na contents were obtained in common in all of the optic chiasma, lateral geniculate body, and superior colliculus. It was examined whether there were significant correlations among the optic chiasma, lateral geniculate body, and superior colliculus in the seven elements and the following results were obtained: There were significant direct correlations between the optic chiasma and lateral geniculate body in both the P and Mg contents; there was a significant direct correlation between the optic chiasma and superior colliculus in the Fe content; and a significant direct correlation was found between the lateral geniculate body and superior colliculus in the Mg content. Regarding the gender differences in elements, it was found that both the Ca and Zn contents of the lateral geniculate body were significantly higher in women than in men.     

Physiological properties of neurons in superficial layers of superior colliculus of rabbits

Neurons in superficial layers of the superior colliculus of the rabbit are classified into three types by their electrophysiological properties. Among them, two types belong to projecting neurons which send axons to the thalamic pulvinar (N=52) and dorsal lateral geniculate nucleus (N = 54) respectively. All other neurons are pooled into the third type (N=99). Projecting neurons of both types receive monosynaptic visual inputs via optic tract fibers of similar conduction velocity, indicating that in the superior colliculus of the rabbit, there is no difference in conduction velocity between the two pathways. They also receive trisynaptic inhibitory inputs, most likely via recurrent inhibitory circuits. The third type of neurons receives disynaptic optic and trisynaptic inhibitory inputs. The function of neurons of the third type is studied.     

Brain-derived neurotrophic factor is an anterograde survival factor in the rat visual system

BACKGROUND: The neurotrophins, which include nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), NT-4/5 and NT-6, are a family of proteins that play fundamental roles in the differentiation, survival and maintenance of peripheral and central neurons. Much research has focused on the role of neurotrophins as target-derived, retrogradely transported trophic molecules. Although there is recent evidence that BDNF and NT-3 can be transported in an anterograde direction along peripheral and central axons, there is as yet no conclusive evidence that these anterograde factors have direct post-synaptic actions. RESULTS: We report that BDNF travels in an anterograde direction along the optic nerve. The anterogradely transported BDNF had rapid effects on retinal target neurons in the superior colliculus and lateral geniculate nucleus of the brain. When endogenous BDNF within the developing superior colliculus was neutralised, the rate of programmed neuronal death increased. Conversely, provision of an afferent supply of BDNF prevented the degeneration of geniculate neurons after removal of their cortical target. CONCLUSIONS: BDNF released from retinal ganglion cells acts as a survival factor for post-synaptic neurons in retinal target fields.     

Pseudorabies virus membrane proteins gI and gE facilitate anterograde spread of infection in projection-specific neurons in the rat

The membrane proteins gI and gE of Pseudorabies virus (PRV) are required for viral invasion and spread through some neural pathways of the rodent central nervous system. Following infection of the rat retina with wild-type PRV, virus replicates in retinal ganglion neurons and anterogradely spreads to infect all visual centers in the brain. By contrast, gI and gE null mutants do not infect a specific subset of the visual centers, e.g., the superior colliculus and the dorsal lateral geniculate nucleus. In previous experiments, we suggested that the defect was not due to inability to infect projection-specific retinal ganglion cells, because mixed infection of a gE deletion mutant and a gI deletion mutant restored the wild-type phenotype (i.e., genetic complementation occurred). In the present study, we provide direct evidence that gE and gI function to promote the spread of infection after entry into primary neurons. We used stereotaxic central nervous system injection of a fluorescent retrograde tracer into the superior colliculus and subsequent inoculation of a PRV gI-gE double null mutant into the eye of the same animal to demonstrate that viral antigen and fluorescent tracer colocalize in retinal ganglion cells. Furthermore, we demonstrate that direct injection of a PRV gI-gE double null mutant into the superior colliculus resulted in robust infection followed by retrograde transport to the eye and replication in retinal ganglion neuron cell bodies. These experiments provide additional proof that the retinal ganglion cells projecting to the superior colliculus are susceptible and permissive to gE and gI mutant viruses. Our studies confirm that gI and gE specifically facilitate anterograde spread of infection by affecting intracellular processes in the primary infected neuron such as anterograde transport in axons or egress from axon terminals.     

An autoradiographic study of the retinal projections in the Formosan monkey

This study investigated the retinal projections of the adult Formosan rock monkey by monocular injection of radioactive proline and fucose. We found that the retinofugal fibers terminated bilaterally in the suprachiasmatic, pregeniculate, lateral geniculate, pretectal complex, pulvinar nucleus, superior colliculus, dorsal and lateral terminal nuclei of the accessory optic system. More crossed retinal terminations were observed, with the exception that the suprachiasmatic nucleus received almost equally of both retinal projections. The existence of the retinal projection to the medial terminal nucleus of the accessory nucleus was in doubt. In the geniculate nucleus, the retinal fibers terminated contralaterally in layers 1, 4 and 6; and ipsilaterally in 2, 3 and 5. In the superior colliculus, most retinal fibers were aggregated superficially in a band located in the contralateral striatum griseum superficialis of the superior colliculus, and had few gaps on the ipsilateral one. The present investigation shows that the Formosan rock monkey has a similar pattern of optic fiber distribution to that of other macaques.     

Axonal transport of actin in rabbit retinal ganglion cells

We labeled proteins in the cell bodies of rabbit retinal ganglion cells with [35S]methionine and subsequently observed the appearance of radioactive actin in tissues containing the axons and synaptic terminals of these neurons, i.e., the optic nerve (ON), optic tract (OT), lateral geniculate nucleus (LGN) and the superior colliculus (SC). The temporal sequence of appearance of labeled actin (which was identified by its specific binding to DNase I, its electrophoretic mobility, and its peptide map) in these tissues indicated that actin is an axonally transported protein with a maximum transport velocity of 3.4--4.3 mm/d. The kinetics of labeling actin were similar to the kinetics of labeling two proteins (M1 and M2) which resemble myosin; these myosin-like proteins were previously found to be included in the groups of proteins (groups III and IV) transported with the third and fourth most rapid maximum velocities. The similarity in transport between actin and myosin-like proteins supports the idea that a number of proteins in the third and fourth transport groups may be functionally related by virtue of their involvement in a force-generating mechanism and suggests the possibility that these proteins may be axonally transported as a preformed force-generating unit.     

Axonal transport of the mitochondria-specific lipid, diphosphatidylglycerol, in the rat visual system

Rats 24 d old were injected intraocularly with [2-3H]glycerol and [35S]methionine and killed 1 h-60 d later. 35S label in protein and 3H label in total phospholipid and a mitochondria-specific lipid, diphosphatidylglycerol(DPG), were determined in optic pathway structures (retinas, optic nerves, optic tracts, lateral geniculate bodies, and superior colliculi). Incorporation of label into retinal protein and phospholipid was nearly maximal 1 h postinjection, after which the label appeared in successive optic pathway structures. Based on the time difference between the arrival of label in the optic tract and superior colliculus, it was calculated that protein and phospholipid were transported at a rate of about 400 mm/d, and DPG at about half this rate. Transported labeled phospholipid and DPG, which initially comprised 3-5% of the lipid label, continued to accumulate in the visual structures for 6-8 d postinjection. The distribution of transported material among the optic pathway structures as a function of time differed markedly for different labeled macromolecules. Rapidly transported proteins distributed preferentially to the nerve endings (superior colliculus and lateral geniculate). Total phospholipid quickly established a pattern of comparable labeling of axon (optic nerve and tract) and nerve endings. In contrast, the distribution of transported labeled DPG gradually shifted toward the nerve ending and stabilized by 2-4 d. A model is proposed in which apparent "transport" of mitochondria is actually the result of random bidirectional saltatory movements of individual mitochondria which equilibrate them among cell body, axon, and nerve ending pools.     

Formation of slow background activity in different parts of the visual analyzer following section of half the tectum mesencephali

Significant changes in the formation of electrical activity rhythms have been revealed in the lateral geniculate body, superior colliculus and visual cortex during section of one half of midbrain operculum in cats anesthetized with nembutal. It was determined that all changes in slow activity generation in the lateral geniculate body, superior colliculus are reflected in changes in the formation of electrical activity of the visual cortex. It is suggested that lateral geniculate body and superior colliculus may be involved in the generation of some electrical activity rhythms of the visual cortex.     

Axonal Transport of Glycoconjugates in the Rat Visual System

Long-Evans rats at 45 days of age were injected intraocularly with 25 mu Ci of [3H]glucosamine. Incorporation of radioactivity into retinal gangliosides, glycoproteins, and glycosaminoglycans (GAGs) was determined at various times after injection. Portions of all three classes of radioactive macromolecules were committed to rapid axonal transport in the retinal ganglion cells. With respect to gangliosides about 60% of those synthesized in the retina were retained in that structure, 30% were committed to transport to regions containing the nerve terminal structures (lateral geniculate body and superior colliculus), and about 10% were deposited in stationary structures of the axons (optic nerve and tract). With the exception of ganglioside GD3 the molecular species distribution of gangliosides synthesized in the retina matched that committed to transport. In contrast to gangliosides a smaller fraction of newly synthesized retinal glycoprotein (less than 12% of that synthesized in the retina) was committed to rapid transport to nerve ending regions and only about 0.5% was retained in the nerve and tract. The molecular-weight distribution of glycoproteins committed to transport differed quantitatively from that of the retina. With respect to GAGs an even smaller portion (1-2%) of that synthesized in the retina was committed to rapid transport; of this portion almost all was recovered in nerve terminal-containing structures. A constant proportion of each retinal GAG species was transported to the superior colliculus. We suggest that most of the retinal gangliosides are synthesized in neurons and preferentially in ganglion cells (possibly a function of the large surface membrane area supported by these cells). Subcellular fractionation experiments indicated that transported gangliosides, glycoproteins, and GAGs may be preferentially distributed into different subcellular compartments.     

Demonstration of retinal afferents in the RCS rat,with reference to the retinohypothalamic projection and suprachiasmatic nucleus

In the Royal College of Surgeons (RCS) rat, characterized by inherited retinal dystrophy, retinal projections to the brain were studied using anterograde neuronal transport of cholera toxin B subunit upon injection into one eye. The respective immunoreactivity was found predominantly contralateral to the injection site in the lateral geniculate nucleus, superior colliculus, nucleus of the optic tract, medial terminal nucleus of the accessory optic tract, and bilateral hypothalamic suprachiasmatic nuclei. Although terminal density was somewhat reduced in dystrophic rats, the projection patterns in these animals appeared similar to those seen in their congenic controls and were comparable to the visual pathways described for the rat previously. In dystrophic rats, the number of cell bodies exhibiting immunoreactivity to vasoactive intestinal polypeptide, viz. a population of suprachiasmatic neurons receiving major retinohypothalamic input, was reduced by one-third, and some differences were observed in the termination pattern of the geniculohypothalamic tract, as revealed by immunoreactivity to neuropeptide Y in the suprachiasmatic nucleus.This study was supported by grants from the DFG (Re 644/2-1) and the NMFZ, Mainz (to S.R.).     

The synaptic distribution of the retinal input in the superficial layers of the guinea-pig superior colliculus

An evoked potential consisting of four postsynaptic components was recorded in the guinea-pig superior colliculus following electrical stimulation of the contralateral optic nerve. This potential was generated in response to the activation of four populations of optic nerve fibres with different conduction velocities. Current source-density analysis revealed that the two slower conducting fibre populations synapse in the upper third of the stratum griseum superficiale on dendrites whose cell bodies appear to be found in the lower part of this layer and in the stratum opticum. The two faster conducting populations synapse deeper, near the border of the stratum griseum superficiale and stratum opticum, on neurons with cell bodies that may lie towards the upper part of the stratum griseum superficiale. The locations of these postsynaptic sites correspond to the layers in which the optic nerve terminates as revealed by neuroanatomical tracing techniques. Furthermore, neurons of the shape and orientation predicted by the current source-density analysis were found in the superficial layers by using the Golgi-Cox technique.     

The effect of M-cholinolytics on the lability of rabbit visual analyzer structures]

The influence of M-cholinolytics (amizyl, glipine, cyclozyl and 4-oxypiperidylbenzylate) in 0.01--10 mg/kg doses on EEG and photic driving in structures of the visual analyser was studied in experiments on twenty intact rabbits with chronically implanted electrodes in the optic chiasm, the optic tract, the lateral geniculate body and the visual cortex. All M-cholinolitics in the doses studied produced synchronization of the EEG. Photic stimulation against the background of small doses of M-cholinolytics (0.01--0.5 mg/kg) did not lead to any disturbances of photic driving. With increased doses of cholinolitics up to 1--5 mg/kg only low frequencies (1--5 imp/sec) produced driving in the lateral geniculate body and the visual cortex, while in the optic tract the driving remained at the initial level. Administration of drugs in a 10 mg/kg dose resulted in complete depression of the driving response in the lateral geniculate body and visual cortex, while in the optic tract the driving was retained.     

Retinofugal projections of the big brown bat, Eptesicus fuscus and the neotropical fruit bat, Artibeus jamaicensis

Retinal connections were studied in Eptesicus fuscus and Artibeus jamaicensis using anterograde axonal degeneration and autoradiographic techniques following unilateral enucleations and uniocular injections of radioactive amino acids. Although each retina projected bilaterally to the brainstem, the number of silver grains in the emulsion of autoradiographs indicated that nearly all fibers in the optic nerve entered the contralateral optic tract. Ipsilaterally, a major portion of the projection ended in the suprachiasmatic nucleus; caudal to the suprachiasmatic nucleus, the amount of label was so small that individual silver grains were counted to determine the location and quantity of label in other ipsilateral nuclei. In both species the retinal projection terminated bilaterally in the suprachiasmatic, dorsal lateral geniculate, ventral lateral geniculate, and pretectal olivary nuclei and contralaterally in the posterior pretectal nucleus, superficial gray layers of the superior colliculus, and nuclei of the accessory optic system. In Eptesicus the projection to the nucleus of the optic tract ended contralaterally, and in Artibeus it ended in this nucleus bilaterally. The results of this study revealed a basic theme in the optic projection of the two ecologically different microchiropterans. The results differed, however, in that the projection was larger and visually related nuclei were better developed in Artibeus. Such variations are presumed to relate to eye size and the relative use of vision by the two chiropterans.     

Primary optic projections in the rabbit. Study using the horseradish peroxidase anterograde labeling technic

The primary visual pathways, in particular those to the lateral geniculate body, of 11 albino and 7 pigmented rabbits, were studied using the method of anterograde labelling with horseradish peroxidase following injection of the tracer into the vitreous body of one eye. A heavy projection to the contralateral dorsal lateral geniculate nucleus was seen in all animals. In both albino and pigmented animals a region devoid of label was present in the medial part of the alpha sector of the nucleus. This region corresponded to a compact, oval or wedge-shaped field of terminal label in the ipsilateral nucleus, which was much heavier in pigmented than in albino rabbits. In the ventral lateral geniculate nucleus, contralateral retinal input was almost entirely confined to the caudal half of the lateral sector of the nucleus, where two laminae of dense terminal label, separated by a less densely labelled area, were oriented parallel to one another and to the optic tract. This bilaminar distribution of retinal afferents to the ventral lateral geniculate nucleus has not been described in previous studies. The ipsilateral projection was to the dorsal part of the lateral sector and was most prominent in pigmented animals. The "intergeniculate leaflet" received a prominent contralateral input in all animals, and a clear ipsilateral input in pigmented animals, which overlapped with the contralateral input. Projections to other primary visual centres (pretectal nuclei, superior colliculus, nuclei of the accessory optic tract) are also described.     

Presynaptic dendrite cells and two other classes of neurons in the superficial layers of the superior colliculus of the chimpanzee

In the superior colliculus of chimpanzee, three classes of neurons can be identified by ultrastructural criteria. They are 1) marginal cells located in the stratum zonale, 2) collicular relay cells in the stratum griseum superficiale and 3) presynaptic dendrite (PSD) cells, i.e., neurons with presynaptic specializations in soma and/or dendrites. PSD cells are the smallest neurons in the stratum griseum superficiale; they have a relatively large, deeply infolded nucleus and a small rim of cytoplasm rich in free ribosomes. PSD cells are sufficiently different from the two other classes of neurons to be reliably identified at the ultrastructural level. They closely resemble presynaptic neurons as described in the lateral geniculate nucleus of other mammalian species. Presynaptic dendrites in continuity with PSD cells are rich in organelles, especially ribosomal cluster, and establish en passage contact with other dendrites. Another type of presynaptic dendrite, poor in organelles, except for bundles of microtubules, could not be traced back to its parent neuron. Homo- or heterogeneity of PSD cells is discussed. No amxon was traced from a PSD cell.     

The effect of the superior colliculus on the function of the contralateral lateral geniculate body in the cat

In acute experiments on rats it was shown that stimulation of the superior colliculus [correction of upper bimounding] leads to the formation in the contralateral lateral geniculate [correction of external geniculated] body of a colliculus-geniculate response. The nature of the changes in a considerable degree is determined by the fact, to which neurones of the lateral geniculate [correction of external geniculated] body, the effect of contralateral superior colliculus [correction of upper bimounding] is addressed.     

Role of the basal ganglia in the occurrence of paradoxical sleep dreams (hypothetical mechanism)

A hypothetical mechanism of the basal ganglia involvement in the occurrence of paradoxical sleep dreams and rapid eye movements is proposed. According to this mechanism, paradoxical sleep is provided by facilitation of activation of cholinergic neurons in the pedunculopontine nucleus as a result of suppression of their inhibition from the output basal ganglia nuclei. This disinhibition is promoted by activation of dopaminergic cells by pedunculopontine neurons, subsequent rise in dopamine concentration in the input basal ganglia structure. striatum, and modulation of the efficacy of cortico-striatal inputs. In the absence of signals from retina, a disinhibition of neurons in the pedunculopontine nucleus and superior colliculus allows them to excite neurons in the lateral geniculate body and other thalamic nuclei projecting to the primary and higher visual cortical areas, prefrontal cortex and back into the striatum. Dreams as visual images and "motor hallucinations" are the result of an increase in activity of definitely selected groups of thalamic and neocortical neurons. This selection is caused by modifiable action of dopamine on long-term changes in the efficacy of synaptic transmission during circulation of signals in closed interconnected loops, each of which includes one of the visual cortical areas (motor cortex), one of the thalamic nuclei, limbic and one of the visual areas (motor area) of the basal ganglia. pedunculopontine nucleus, and superior colliculus. Simultaneous modification and modulation of synapses in diverse units of neuronal loops is provided by PGO waves. Disinhibition of superioir colliculus neurons and their excitation by pedunculopontine nucleus lead to an appearance of rapid eye movements during paradoxical sleep.     

THE TOXIC EFFECT OF SODIUM GLUTAMATE ON RAT RETINA: CHANGES IN PUTATIVE TRANSMITTERS AND THEIR CORRESPONDING ENZYMES

Abstract– Subcutaneous administration of high doses of sodium glutamate to rats during their first week after birth produced an almost total loss of choline acetyltransferase, a 90% reduction in glutamate decarboxylase and 70% reductions in acetylcholinesterase and DOPA decarboxylase activities in the adult retina. In addition there was a 70% decrease in GABA and 35-55% decrease in aspartate, glutamate, glycine, alanine and glutamine. No reduction in taurine was observed. The results support the view that the enzymes are mainly localized in the interneurons of retina and that taurine is present in the photoreceptor cells.
Glutamate treatment was also followed by a small reduction in choline acetyltransferase and glutamate decarboxylase of the superior colliculus and in choline acetyltransferase of hippocampus, whereas no changes could be detected in the lateral geniculate body of the adult rat. Unilateral enucleation performed on 1-day-old animals did not alter choline acetyltransferase, acetylcholinesterase, glutamate decarboxylase and DOPA decarboxylase activities in the superior colliculus and in the lateral geniculate body of the adult rat.     

Control of conduction of afferent impulses across the lateral geniculate body by the side of the superior colliculus in alert rabbits

On alert rabbits it was shown that the stimulation of the superior colliculus inhibit visual evoked potential both of the ipsi- and contralateral geniculate body. Besides, the suppression of amplitude of the contralateral geniculate body's evoked potential was more significant than amplitude of the ipsilateral geniculate body's evoked potential. On the basis of the obtained results the authors suppose that superior colliculus is involved in organization of the effect of saccadic suppression of lateral geniculate body's visual responses.     

The identification of two intra-axonally transported polypeptides resembling myosin in some respects in the rabbit visual system

Two polypeptides (M1 and M2) which co-sediment with F-actin in an ATP- reversible way have been detected in extracts of tissue from the rabbit visual system. Both polypeptides resemble skeletal muscle myosin in their ATP-sensitive co-sedimentation with actin, while they resemble the heavy chain of myosin and the lighter polypeptide of erythrocyte spectrin in their electrophoretic mobilities. (The estimated molecular weights are: MI congruent to 195,000; myosin congruent 200,000; M2 and spectrin congruent to 220,000). M1 and M2 were labeled in the cell bodies of the retinal ganglion cells with a radioactive amino acid and subsequently recovered in tissues (optic nerve, optic tract, lateral geniculate nucleus, and superior colliculus) containing segments of the retinal ganglion cell axons. The temporal sequence of labeling M1 and M2 in these tissues indicated that both polypeptides were synthesized in the cell bodies of retinal ganglion cells and subsequently transported down their axons at different maximum velocities. The estimated velocities were: M1, 4-8 mm per day; and M2, 2-4 mm per day.