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Glutamate spillover between mammalian cone photoreceptors.
- Source :
-
The Journal of neuroscience : the official journal of the Society for Neuroscience [J Neurosci] 2011 Sep 21; Vol. 31 (38), pp. 13431-41. - Publication Year :
- 2011
-
Abstract
- Cone photoreceptors transmit signals at high temporal frequencies and mediate fine spatial vision. High-frequency transmission requires a high rate of glutamate release, which could promote spillover to neighboring cells, whereas spatial vision requires that cones within a tightly packed array signal light to postsynaptic bipolar cells with minimal crosstalk. Glutamate spread from the cone terminal is thought to be limited by presynaptic transporters and nearby glial processes. In addition, there is no ultrastructural evidence for chemical synapses between mammalian cones, although such synapses have been described in lower vertebrate retinas. We tested for cone-cone glutamate diffusion by recording from adjacent cone pairs in the ground squirrel retina, and instead found that the glutamate released by one cone during electrical stimulation activates glutamate transporter Cl(-) conductances on neighboring cones. Unlike in other systems, where crosstalk is diminished by increasing the temperature and by moving to a more intact preparation, glutamate spread persisted at physiological temperatures (37°C) and in retinal flat mounts. The glutamate-gated anion conductance in cones has a reversal potential of ∼-30 mV compared with a cone resting potential of ∼-50 mV; thus, crosstalk should have a depolarizing effect on the cone network. Cone-cone glutamate spread is regulated by the physiological stimulus, light, and under physiological conditions can produce a response of ∼2 mV, equivalent to 13-20% of a cone's light response. We conclude that in the absence of discrete chemical synapses, glutamate flows between cones during a light response and may mediate a spatially distributed positive feedback.
- Subjects :
- Amino Acid Transport System X-AG physiology
Animals
Chloride Channels physiology
Electric Stimulation methods
Membrane Potentials physiology
Patch-Clamp Techniques methods
Photic Stimulation methods
Receptor Cross-Talk physiology
Retina metabolism
Retina physiology
Sciuridae
Glutamic Acid metabolism
Retinal Cone Photoreceptor Cells metabolism
Synaptic Transmission physiology
Vision, Ocular physiology
Subjects
Details
- Language :
- English
- ISSN :
- 1529-2401
- Volume :
- 31
- Issue :
- 38
- Database :
- MEDLINE
- Journal :
- The Journal of neuroscience : the official journal of the Society for Neuroscience
- Publication Type :
- Academic Journal
- Accession number :
- 21940436
- Full Text :
- https://doi.org/10.1523/JNEUROSCI.2105-11.2011