Rabbit Retinal Ganglion Cells Research Articles

Specific effects of neurotransmitter antagonists on ganglion cells in rabbit retina.

Directionally sensitive ganglion cells in rabbit retina lose their directional sensitivity when picrotoxin, an antagonist of the inhibitory neurotransmitter gamma-aminobutyric acid, is infused into the retinal blood supply. Strychnine, an antagonist of glycine, does not produce this effect. Other receptive field types are affected by strychnine but not picrotoxin. Inhibitory transmitters therefore have specific functions in information processing in the retina.

Paracrystalline inclusions in optic nerve terminals following intraocular injection of vinblastine

Intraocular injection of vinblastine sulfate (VLB) at a dose of 10–500 μg disrupts microtubules and blocks rapid axoplasmic transport in the rabbit retinal ganglion cells (GCs). A dose of 500 μg VLB produces characteristics Vinca alkaloid paracrystals in the GCs by 24 h, and unusual paracrystals are noted within optic nerve terminals in the contralateral superior colliculus at survival times of 3, 7 and 14 days. These paracrystals are composed of hexagonally arranged unit structures measuring approximately 55 nm in diameter, and each unit is resolved as a central 25 nm tubule circled by five 15 nm subunits. The paracrystals are surrounded by spherical 50 nm synaptic vesicles, and usually lie adjacent and parallel to the large, pale mitochondria which characterize the optic terminals. The possible significance of the paracrystals is discussed; they may represent an unusual form of neuronal degeneration, an atypical VLB product, or an accumulation of virus particles. Degenerative changes, including enlarged synaptic vesicles and slightly increased background density, were noted in some optic terminals at 7 days following injection of 10–250 μg of VLB. These changes were reversible, and the terminals appeared normal after resumption of rapid axoplasmic transport. These morphologic alterations in the optic terminals may reflect the lack of materials synthesized in the GC perikarya and conveyed to the terminals by rapid axoplasmic transport.

Direction-selective retinal ganglion cells and control of optokinetic nystagmus in the rabbit

Approximately 25 per cent of the rabbit's retinal ganglion cells are directionselective. These cells respond maximally to movement of a visual stimulus in a particular (“preferred”) direction. The class of direction-selective cells can be further subdivided into two groups; the “on-off” and “on-type” direction-selective cells. It has been suggested that the on-off cells may play a role in controlling the slow phase of optokinetic nystagmus. To test this hypothesis, we determined how the responses of directionselective cells, of both types, varied as a function of stimulus velocity. The stimulus was similar to those normally used to elicit nystagmus i.e. a continuous black and white striped grating. The velocity response curves for the direction-selective cells were compared to data on the open loop eye movement velocity of the slow phase of optokinetic nystagmus in rabbits. The results of this comparison indicate that the slow phase is primarily controlled by the on-type direction-selective cells with a secondary contribution from on-off cells at higher stimulus velocities.

Rapid intracellular transport of fucose-containing glycoproteins in retinal ganglion cells.

Abstract[3H]Fucose was incorporated into glycoproteins in the rabbit retinal ganglion cells and subsequently transported at a rapid rate along the optic pathway to the nerve terminals of the lateral geniculate body and the superior colliculus. Radioautographic results indicated a preferential labelling of the terminal part of the axon. Cell fractionation showed that the major part of the transported fucose‐containing glycoproteins were associated with membranes. Sodium dodecy 1 sulphate electrophoresis of rapidly transported glycoproteins showed that most of the polypeptides had a mol. wt. of more than 40,000.

The analysis of image motion by the rabbit retina.

1. Micro-electrode recordings were made from rabbit retinal ganglion cells or their axons. Of particular interest were direction-selective units; the common on-off type represented 20.6% of the total sample (762 units), and the on-type comprised 5% of the total.2. From the large sample of direction-selective units, it was found that on-off units were maximally sensitive to only four directions of movement; these directions, in the visual field, were, roughly, anterior, superior, posterior and inferior. The on-type units were maximally sensitive to only three directions: anterior, superior and inferior.3. The direction-selective unit's responses vary with stimulus velocity; both unit types are more sensitive to velocity change than to absolute speed. On-off units respond to movement at speeds from 6'/sec to 10 degrees /sec; the on-type units responded as slowly as 30''/sec up to about 2 degrees /sec. On-type units are clearly slow-movement detectors.4. The distribution of direction-selective units depends on the retinal locality. On-off units are more common outside the ;visual streak' (area centralis) than within it, while the reverse is true for the on-type units.5. A stimulus configuration was found which would elicit responses from on-type units when the stimulus was moved in the null direction. This ;paradoxical response' was shown to be associated with the silent receptive field surround.6. The four preferred directions of the on-off units were shown to correspond to the directions of retinal image motion produced by contractions of the four rectus eye muscles. This fact, combined with data on velocity sensitivity and retinal distribution of on-off units, suggests that the on-off units are involved in control of reflex eye movements.7. The on-off direction-selective units may provide error signals to a visual servo system which minimizes retinal image motion. This hypothesis agrees with the known characteristics of the rabbit's visual following reflexes, specifically, the slow phase of optokinetic nystagmus.