Rat Visual System Research Articles

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.

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

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

Cortical representation of nonclassical parts of the visual system.

Cortical evoked potentials and extracellular evoked neuronal activity have been investigated in unanesthetized d-curarine immobilized rats during stimulation of the superior colliculi. The focus of responses was found in the lateral part of the visual neocortex (area 18a according to Krieg [5]). The evoked potential includes a negative and subsequent positive waves, its latency being equal to 7.9 +/- 2.8 msec. With deepening the electrode the amplitude of the response decreases, although its polarity remains unchanged. The neuronal activity is of phasic character. During simultaneous record of the evoked potentials and neuronal activity, temporal correlation between impulse activity and the ascending part of the main negative wave of the EP is observed. The data obtained indicate imcomplete overlapping of the retino-geniculo-cortical and retino-tecto-thalamo-cortical channels in the visual system of rats.

Development of rat visual system after prenatal X-irradiation

Summary Rats pregnant for 16 or 19 days (ED 16 or 19) were irradiated with 100 r and killed after 24 hrs or at age 24 or 180 days. The primary influence of X-rays consists in a lethal lesion of cells located in the periventricular zone as well as some of the more differentiated cells in the brain parenchyma. After irradiation on ED 16, the acute damage was greater in the cerebral cortex and the superior colliculus (SC) than in the lateral geniculate nucleus (LGN). Irradiation on ED 19 damaged mainly the cortical part of the visual system. The degree of acute damage is therefore inversely proportional to the degree of histo- and cytodifferentiation of the visual centres (Bruckner et ai. 1976). In adult animals the acute radiation damage results in a deficit in packing density and the total number of neurons. Animals irradiated on ED 16 revealed more pronounced changes in deep layers of the cortex (L VI) than in the superficial layers. The deficit was smaller in the SC, and in the LGN an increase in the packing density of nerve cells was found. In animals irradiated on ED 19, the deficit in neurons density occurred mainly in more superficial layers of the cortex, with a maximum deficit in layer IV. From comparison of acute and final changes it may be concluded that the damage of preneuroblastic cell populations is compensated during later embryonic development, while the damage induced in populations already at early neuroblast stage is irreversible and leads to a permanent deficit. Glia cell population is altered in a similar way as the number of neurons in regions poor in myelin, while in regions rich in myelin the number of glia cells seems to depend on changes in the number of efferent and afferent nerve fibres.

Axonal transport and metabolism of [ 3H]fucose- and [ 35S]- Sulfate-labeled macromolecules in the rat visual system

The axonal transport of labeled macromolecules in retinal ganglion cells of rats was investigated from 1 to 20 days following intraocular injection of [ 3H]fucose and [ 35S]sulfate. Maximal incorporation of [ 3H]fucose into acid insoluble material in the retina was at 8 h, followed by a biphasic decline. Transported [ 3H]fucose (98% as glycoprotein) was in the optic nerve at 1 h, the optic tract and lateral geniculate body by 2 h, and the superior colliculus by 3 h after injection, indicating a rate of transport of approximately 200 mm/day. Radioactivity continued to accumulate in the superior colliculus for at least 8 h and began to decline rapidly by 24 h. Between 3 and 6 days levels rose again in both optic tract and superior colliculus before starting a gradual decline, indicating that a wave of rapidly transported material was delayed in leaving the retina. When proteins in the superior colliculus were fractionated by gel electrophoresis, the composition of the two fucosylated protein transport phases could be partially resolved. Radioactivity in individual gel peaks represented primarily in the first phase decayed with an average half-life of one day, although that in one prominent protein of molecular weight 280,000 turned over with a half-life of the order of 12 h. Radioactive peaks primarily in the second phase decayed with an average half-life of more than a week. Incorporation of [ 35S]sulfate into acid insoluble material in the retina was maximal at 1–2 h, after which there was a rapid loss of label. The appearance of [ 35S]sulfate in the optic tract, loateral geniculate body and superior colliculus preceded by a short time that of the [ 3H]fucose; indicating a shorter retinal processing time for this label. The total transported [ 35S]sulfate in the superior colliculus peaked by 4–8 h and had fallen by 65% at one day; no prominent second wave of transport was observed as was the case for [ 3H]fucose. Acid insoluble [ 35S]sulfate in the superior colliculus was equally divided between glycopeptides and glycosaminoglycans at all times examined, indicating that these macromolecules are transported at the same rate. [ 35S]Sulfate incorporated into various proteins fractionated by gel electrophoresis had heterogeneous turnover rates, the average being around 12 h. Radioactivity in one group of proteins, of molecular weight around 90,000, decayed with a half-life of only a few hours.

Axonal transport of nucleosides, nucleotides and 4S RNA in the neonatal rat visual system

The axonal migration of RNA, the nucleoside uridine and its nucleotide derivates (NS/NT) were compared in neonatal and young adult rat optic axons. Tritiated uridine was injected into right eyes of developing (1- or 4-day-old) and young adult (40-day-old) rats which were sacrificed at times after injection ranging from 6 h to 20 days. Right and left lateral geniculates were removed and assayed for trichloroacetic acid soluble (NS/NT) and RNA radioactivity. Left minus right geniculate (L-RLG) radioactivity was used as an index of axonally migrating radioactivity. Results showed that uridine and its phosphorylated derivatives were transported along both neonatal and young adult rat optic axons. Greater than 90% of right geniculate (blood-borne) TCA soluble radioactivity was metabolized to volatile substances (probably 3H2O) by three days after injection, leaving approximately 3% of the neonatal and approximately 10% of the adult activity as [3H]NS/NT. In left geniculate fractions (containing transported material) approximately 15% and 40% of total TCA soluble radioactivity was present as [3H]NS/NT in neonates and adults, respectively. Thus, axonal NS/NT appears to be relatively protected from degradation when compared with blood-borne NS/NT. The amount of L-RLG [3H]RNA in the neonates was 10 times higher than in young adults. Peaks of neonatal [3H]RNA occurred at 5 and 10 days after birth, whether injections were made at 1 or 4 days of age indicating that this [3H]RNA may be linked to developmental events. Gel electrophoretic analysis of neonatal geniculate RNA indicated that a small portion of the [3H]RNA in the first peak represented axonally transported 4S RNA. The remainder of the L-RLG [3H]RNA in the neonates was probably due to a rapid and efficient incorporation of axonally transported [3H]NS/NT into extraaxonal geniculate RNA. In contrast, little or no axonal RNA transport could be demonstrated in the young adults.

Axonal transport of phospholipids in rat visual system.

Abstract— Seventeen day old rats were injected intraocularly with a phospholipid precursor, [32P]phosphate, and a glycoprotein precursor, [3H]fucose. Animals were killed between 1 h and 21 days later, and structures of the visual pathway (retina, optic nerve, optic tract, lateral geniculate body, and superior colliculus) were dissected. Radioactivity in phospholipids ([32P] in solvent‐extracted material) and in glycoproteins ([3H] in solvent‐extracted residue) was determined. Incorporation of [3H]fucose into retinal glycoproteins peaked at 6–8 h. Labelled glycoproteins were present in superior colliculus by 2h after injection, indicating a rapid rate of transport; maximal labelling was at 8–10 h after injection. Incorporation of [32P]phosphate into retinal phospholipids peaked at 1 day after injection. Phospholipids were also rapidly transported since label was present in the superior colliculus by 3 h after injection: however, maximal labelling did not occur until 5–6 days. These results indicate that newly synthesized phospholipids enter a preexisting pool, part of which is later committed to transport at a rapid rate.Transported phospholipids were catabolized at the nerve endings with a maximum half‐life of several days; there was minimal recycling of precursor label.Lipids were fractionated by thin‐layer chromatography, and radioactivity in individual phospholipid classes determined. Choline and ethanolamine phosphoglycerides were the major transported phospholipids, together accounting for approx 85% of the total transported lipid radioactivity. At early time points, the ratio of radioactivity in choline phosphoglycerides to that in ethanolamine phosphoglycerides increased in structures progressively removed from the site of synthesis (retina) but by 2 days approached a constant value. In each structure, choline phosphoglyceride‐ethanolamine phosphoglyceride radioactivity ratios decreased with time, rapidly at first, but plateaued by 2 days. These results indicate that choline phosphoglycerides are committed to transport sooner than ethanolamine phosphoglycerides.Some experiments were also conducted using [2‐3H]glycerol as a phospholipid precursor. Results concerning incorporation of this precursor into individual phospholipid classes and their subsequent axonal transport were comparable to those obtained using [32P]phosphate, with the following exceptions: (a) incorporation of [2‐3H]glycerol into retinal phospholipids was relatively rapid (near‐maximal levels at 1 h after injection) although transport to the superior colliculus showed an extended time course very similar to [32P]‐labelled lipids; (b) [2‐3H]glycerol was somewhat less efficient than [32P]phosphate in labelling lipids committed to transport relative to labelling those which remained in the retina; and (c) [2‐3H]glycerol did not label plasmalogens.

Early selective visual experience and pattern discrimination in hooded rats.

The early visual experience of hooded rats was restricted to either vertical or horizontal stripes. In a discrimination task pairing a gray surface and stripes of either the same orientation or an orientation orthogonal to that experienced during rearing, the rats made significantly fewer correct choices with the orthogonal orientation. However, the relatively lower overall performance of the vertically reared-horizontally tested animals was a major factor in the main effect of testing condition. We conclude that functional of the rat visual system through early selective visual experience is possible.

Features of foreign proteins affecting their retrograde transport in axons of the visual system.

The retrograde axoplasmic transport of foreign proteins in the rat visual system shows certain specificities. The molecular features of these proteins which may underlie their entry into the retrograde phase have been examined using biochemical and morphologic techniques. Of the isoenzymes of horseradish peroxidase (HRP), the basic isoenzyme C is strongly transported, while the acidic isoenzymes Abeta and Aalpha are transported weakly and not at all, respectively. Decreasing the isoelectric point (pI) of isoenzyme C from 8.2 to 4.4 decreases its transport, but a basic pI is not the sole requisite for transportability since two other basic peroxidases (turnip isoenzyme P7 and lactoperoxidase) are not transported in retrograde. The sugar component as a whole of isoenzyme C does not appear to be required for determining transport. Isoenzyme C and the other proteins which are transported enter multivesicular bodies in axons and axon terminals, as well as synaptic and coated vesicles and fine tubules in axon terminals. The non-transported proteins enter only the vesicular organelles thought to be involved in neurotransmitter recycling in axon terminals and do not enter multivesicular bodies. Thus the two systems of axonal membraneous compartments involved in local synaptic recycling versus the retrograde phase of transport do not show the same specificity of uptake of extracellular tracers and can be dissociated by the experimental use of these peroxidases.

Influence of systemic factors on hyperbaric oxygen toxicity in the rat visual system

Influence of systemic factors on hyperbaric oxygen toxicity in the rat visual system

Anatomical and neurobehavioral investigations concerning the thalamo-cortical organization of the rat's visual system.

The organization of thalamic afferents to the rat's visual cortex was investigated autoradiographically and through the retrograde transport of horseradish peroxidase (HRP) following infections into striate and peristriate cortex. The results revealed that Nucleus lateralis posterior (NLP) projects to a large peristriate cortical field that includes areas 18A, 7, and the anterior portion of area 18, and to a circumscribed temporal area corresponding to Krieg's ('46a,b) area 20. The dorsal lateral geniculate nucleus (LGNd) was shown to project to two spatially discontinuous cortical areas. The largest geniculate receiving area is partially coextensive with Krieg's area 17, but an extension of this projection posterior and medial to the striate cortex was found. In addition, a geniculate projection to a restricted field located in the lateral peristriate cortex was identified. Concurrent investigations were designed to assess the pattern discrimination abilities of rats prepared with striate cortical ablations, lesions in NLP and combined striate-cortical and thalamic ablations. Comparison of these animals with normal control subjects revealed that the striate cortex in the rat (as in the cat [Doty, '71; Sprague et al., '77] and the tree shrew [Killackey and Diamond, '71; Ware et al., '74]) is not necessary for successful pattern discrimination, and that the geniculo-striate and NLP-extra-striate projection systems are both involved in mediating the visual discriminative abilities of the rat. The results add species generality to the concept that the central connections to the visual cortex are characterized by parallel-conducting thalamic channels and contribute to the growing number of demonstrations that the extra-striate cortex and associated thalamic cell groups contribute significantly to the process of visual-pattern recognition.

Tectocortical connections in the rat visual system.

Electrical stimulation of the superior colliculus by square pulses evokes responses in the ipsilateral occipital region whose localization coincides with the zone of evoked potentials to photic stimulation. The short latent period of the visual cortical evoked potentials to stimulation of the superior colliculus (mean 3.2 +/- 1.1 msec; P less than 0.05) together with morphological data suggests that only one relay, in the structures of the thalamus, occurs along the tectocortical pathway in the rat visual system. In the poorly differentiated cortex of the rat no separate representation of retino-geniculo-cortical and tectocortical channels could be found.

Delineation of the rat visual system by the axonal iontophoresis-cobalt sulfide precipitation technique

Delineation of the rat visual system by the axonal iontophoresis-cobalt sulfide precipitation technique

Effects of harmaline on the visual system of the rat

Harmaline is a potent hallucinogenic drug as demonstrated by clinical studies. The purpose of this work was to study the effect of Harmaline on some electrophysiological responses at various levels of the rat visual system. The intravenous injection of 2 mg/kg provokes typical changes of the ERG in the albino rat. The late receptor potential is enhanced both in magnitude and duration. The b-wave amplitude diminishes, while its duration increases. Another characteristics effects of the drug on the b-wave is the appearance of additional rapid oscillatory wavelets. Evoked responses elicited by electrical stimulation of the optic nerve in the dorsal lateral geniculate nucleus, were reversibly abolished by intra-arterial injection of 2–8 mg/kg of Harmaline. The suppression of presynaptic potentials in the dorsal lateral geniculate nucleus indicates that this hallucinogen diminishes the excitability of the optic nerve fibers. This anaesthetic property of Harmaline was also observed in the Saphenous nerve. Intravenous injection of the drug augments both threshold and latency, and reduces the size of the action potential. Experiments performed in squid axons demonstrated that Harmaline reversibly decrease, Na conductance without altering K conductance.

Influence of visual cortex on receptive fields in the superior colliculus of the cat.

Influence of visual cortex on receptive fields in the superior colliculus of the cat.

Relation of the visual field to the lateral geniculate body of the albino rat.

Relation of the visual field to the lateral geniculate body of the albino rat.

AUTORADIOGRAPHIC AND HISTOLOGICAL INVESTIGATION OF CHANGES IN THE VISUAL SYSTEM OF RATS AFTER UNILATERAL ENUCLEATION.

AbstractFollowing surgical removal of one eye, rats were permitted to survive for three days, one, two and four months, and before killing them they were injected with 2 mc of leucine‐H3 intraperitoneally. The utilization of this radiochemical was investigated in the brain autoradiographically. In all groups of animals the uptake of radioleucine, as determined by microdensitometry, was significantly higher in the “degenerated” optic nerve and tract than in their “normal” counterparts, with the relative difference increasing with longer postoperative survival within the periods tested. This progressive net increase in the utilization of leucine‐H3 was associated with an absolute increase in the number of glia cells. Similar, but attenuated, density differences were also obtained with relatively large‐aperture measurements over the stratum griseum of the superior colliculus in which the optic tract fibers terminate. In contrast, small‐aperture measurements of grain density over single neurons in the lateral geniculate nucleus showed no difference in the utilization of leucine‐H3 between the normal and subtotally deafferented sides. This suggests an absence of transneuronal changes in protein metabolism in the visual system of the rat as long as four months after unilateral enucleation.