Synaptic Mechanisms Regulating the Activation of a Ca2+-Mediated Plateau Potential in Developing Relay Cells of the LGN

2002 ◽  
Vol 87 (3) ◽  
pp. 1175-1185 ◽  
Author(s):  
Fu-Sun Lo ◽  
Jokubas Ziburkus ◽  
William Guido
Keyword(s):  
Retinal Ganglion Cells ◽  
Temporal Summation ◽  
Ganglion Cells ◽  
Optic Tract ◽  
Receptor Activity ◽  
Dorsal Lateral Geniculate Nucleus ◽  
Retinal Ganglion ◽  
Plateau Potential ◽  
Age Related ◽  
Stimulation Of

Using intracellular recordings in an isolated (in vitro) rat brain stem preparation, we examined the synaptic responses of developing relay neurons in the dorsal lateral geniculate nucleus (LGN). In newborn rats, strong stimulation of the optic tract (OT) evoked excitatory postsynaptic potentials (EPSPs) that gave rise to a sustained (300–1,300 ms), slow-decaying (<0.01 mV/s), depolarization (25–40 mV). Riding atop this response was a train of spikes of variable amplitude. We refer to this synaptically evoked event as a plateau potential. Pharmacology experiments indicate the plateau potential was mediated by the activation of high-threshold L-type Ca2+ channels. Synaptic activation of the plateau potential relied on N-methyl-d-aspartate (NMDA) receptor-mediated activity and the spatial and/or temporal summation of retinally evoked EPSPs. Inhibitory postsynaptic responses (IPSPs) did not prevent the expression of the plateau potential. However, GABAA receptor activity modulated the intensity of optic tract stimulation needed to evoke the plateau potential, while GABAB receptor activity affected its duration. Expression of the plateau potential was developmentally regulated, showing a much higher incidence at P1–2 (90%) than at P19–20 (1%). This was in part due to the fact that developing relay cells show a greater degree of spatial summation than their mature counterparts, receiving input from as many as 7–12 retinal ganglion cells. Early spontaneous retinal activity is also likely to trigger the plateau potential. Repetitive stimulation of optic tract in a manner that approximated the high-frequency discharge of retinal ganglion cells led to a massive temporal summation of EPSPs and the activation of a sustained depolarization (>1 min) that was blocked by L-type Ca2+ channel antagonists. These age-related changes in Ca2+ signaling may contribute to the activity-dependent refinement of retinogeniculate connections.

Pathways of regenerated retinotectal axons in goldfish

Development ◽  
1986 ◽  
Vol 93 (1) ◽  
pp. 1-28
Author(s):  
Claudia A. O. Stuermer
Keyword(s):  
Optic Nerve ◽  
Retinal Ganglion Cells ◽  
Normal Development ◽  
Ganglion Cells ◽  
Optic Tract ◽  
Spatiotemporal Pattern ◽  
Retinal Ganglion ◽  
Retinal Axons ◽  
Age Related ◽  
Regenerated Fibres

This study investigates the order of regenerating retinal axons in the goldfish. The spatiotemporal pattern of axon regrowth was assessed by applying horseradish peroxidase (HRP) to regenerating axons in the optic tract at various times after optic nerve section and by analysing the distribution of retrogradely labelled ganglion cells in retina. At all regeneration stages labelled ganglion cells were widely distributed over the retina. There was no hint that axons from central (older) ganglion cells might regrow earlier, and peripheral (younger) ganglion cells later, as occurs in normal development. The absence of an age-related ordering in the regenerated optic nerve was demonstrated by labelling a few axon bundles intraorbitally with HRP (Easter, Rusoff & Kish, 1981) caudal to the previous cut. The retrogradely labelled cells in retina were randomly distributed in regenerates andnot clustered in annuli as in normals. Tracing regenerating axons which were stained anterogradelyfrom intraretinal HRP applications or retrogradely from single labelled tectal fascicles illustrated the fact that the regenerating axons coursed in abnormal routes in the optic nerve and tract. On the surface of the tectum regenerated fibres re-established a fascicle fan. The retinal origin of tectal fascicles was assessed by labelling individual peripheral, intermediate and rostral fascicles with HRP. The retrogradely labelled ganglion cells in the retina were often more widely distributed than in normals, but were mostly found in peripheral, intermediate and central retina, respectively. The order of fibre departure from each tectal fascicle was revealed by placing HRP either on the fascicle's proximal or on its distal half. With proximal labelling sites labelled ganglion cells were found in the temporal and nasal retina, and with distal labelling sites labelled ganglion cells were confined to nasal retina only. Further, the axonal trajectories of anterogradely labelled dorsotemporal retinal ganglion cells were compared to those of dorsonasal retinal ganglion cells in tectal whole mounts. Dorsotemporal axons were confined to the rostral tectal half, whereas dorsonasal axons followed fascicular routes into the fascicles' distal end and reached into caudal tectum. This suggests that the fibres exited along their fascicle's course in a temporonasal sequence. Thus in the tectum, fibres in fascicles restore a gross spatial and age-related order and tend to follow their normal temporonasal sequence of exit.

Superior colliculus cell responses to electrical stimulation of the retina

1977 ◽  
Vol 55 (2) ◽  
pp. 301-306 ◽  
Author(s):  
S. Molotchnikoff ◽  
P. L'archevêque
Keyword(s):  
Electrical Stimulation ◽  
Superior Colliculus ◽  
Retinal Ganglion Cells ◽  
Ganglion Cells ◽  
Optic Tract ◽  
Retinal Ganglion ◽  
Cell Responses ◽  
Prolonged Discharge ◽  
Stimulation Of

Superior colliculus cell discharges in response to electrical stimulation of the retina were investigated in rabbit. In contrast with the responses at the optic tract level both polarities evoked discharges of equal latencies suggesting a convergence of ON- and OFF-centre retinal ganglion cells upon one collicular unit. Three typical patterns of responses could be distinguished. Thus, 40% of cells reacted with a burst, 47% with a prolonged discharge, and 5% responded by a transient inhibition. The responses of the remaining cells could not be classified.

scholarly journals Stimulation of the P2X7 receptor kills rat retinal ganglion cells in vivo

2010 ◽  
Vol 91 (3) ◽  
pp. 425-432 ◽  
Author(s):  
Huiling Hu ◽  
Wennan Lu ◽  
Mei Zhang ◽  
Xiulan Zhang ◽  
Arthur J. Argall ◽  
...  
Keyword(s):  
Retinal Ganglion Cells ◽  
P2x7 Receptor ◽  
Ganglion Cells ◽  
Retinal Ganglion ◽  
Stimulation Of

Abnormally high variability in the uncrossed retinofugal pathway of mice with albino mosaicism

Development ◽  
1987 ◽  
Vol 101 (4) ◽  
pp. 857-867 ◽  
Author(s):  
R.W. Guillery ◽  
G. Jeffery ◽  
B.M. Cattanach
Keyword(s):  
Retinal Ganglion Cells ◽  
Ganglion Cells ◽  
Gene Dosage ◽  
Optic Tract ◽  
High Variability ◽  
Retinal Ganglion ◽  
Rare Occurrence ◽  
Autosome Translocation ◽  
Open Question ◽  
The Relationship

Female mice showing albino mosaicism due to an X-autosome translocation [Is(In7;X)Ct] have been studied in order to investigate the relationship between the distribution of melanin and the formation, early in development, of the abnormally small uncrossed retinofugal pathway characteristically found in all albino mammals. Earlier evidence indicates that cells normally bearing melanin play a role in producing the abnormality. In the mosaic mice, the albino gene is expressed in only about half of the cells due to random X-inactivation and the patches of normal and albino cells are extremely small relative to total retinal size (less than 1/50). We argued that if all the cells that would normally bear melanin play a role in producing the albino abnormality then the mosaic mice would have a pathway abnormality, about half the size of that in the albino mice. If, however, only a small patch of these cells plays a role, as has been proposed in earlier studies, then one would expect the size of the uncrossed pathway to be highly variable in the mosaic mice. The size of the uncrossed pathway was assessed by placing horseradish peroxidase in the region of the optic tract and lateral geniculate nucleus unilaterally and then counting the number of retrogradely labelled retinal ganglion cells on the same side. The mosaic mice showed a highly variable uncrossed pathway. In some of the mosaic mice, it was the same size as in the albinos and, in others, it was the same size as in normally pigmented mice. Surprisingly, in a small number of mosaic mice, the uncrossed pathway was larger than normal. Whether this relatively rare occurrence of a supernormal uncrossed pathway is due to the higher gene dosage or to the translocation itself remains an open question.

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