| Complementary roles of two excitatory pathways in retinal directional selectivity. | |
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MedLine Citation:
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PMID: 9839976 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The two major excitatory synapses onto ON-OFF directionally selective (DS) ganglion cells of the rabbit retina appear to be nicotinic cholinergic and NMDA glutamatergic. Blockade of either of these synapses with antagonists does not eliminate directional selectivity. This suggests that these synapses may have complementary roles in the computation of the direction of motion. To test this hypothesis, quantitative features of the DS cell excitatory pathways were determined by collecting responses, under nicotinic and/or NMDA blockade, to a sweeping bar, hyperacute apparent motions, or a drifting sinusoidal grating. Sweeping bar responses were reduced, but directional selectivity not eliminated, by blockade of either excitatory path, as previously shown (Cohen & Miller, 1995; Kittila & Massey, 1997). However, residual responses under combined blockades were not statistically significantly DS. NMDA blockade reduced responses more than nicotinic blockade for each protocol, and shifted hyperacute motion thresholds to higher values. This supported the notion that glutamate provides the main excitatory drive to DS cells, that is, the one responsible for contrast sensitivity. In turn, nicotinic, but not NMDA blockade eliminated directional selectivity to a drifting low spatial-frequency sinusoidal grating in these cells. This suggested that acetylcholine (ACh) is the main excitatory input with regards to directional selectivity for some textured stimuli, that is, those with multiple peaks in their spatial luminance profile. Moreover, nicotinic blockade raised the low temporal-frequency cutoff of the grating responses, consistent with the proposal that preferred-direction facilitation, which is temporally sustained, is dependent on the cholinergic input. These different properties of the NMDA and nicotinic pathways are consistent with a recently proposed two-asymmetric-pathways model of directional selectivity. |
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Authors:
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N M Grzywacz; D K Merwine; F R Amthor |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
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Title: Visual neuroscience Volume: 15 ISSN: 0952-5238 ISO Abbreviation: Vis. Neurosci. Publication Date: 1998 Nov-Dec |
Date Detail:
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Created Date: 1999-02-26 Completed Date: 1999-02-26 Revised Date: 2007-11-14 |
Medline Journal Info:
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Nlm Unique ID: 8809466 Medline TA: Vis Neurosci Country: ENGLAND |
Other Details:
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Languages: eng Pagination: 1119-27 Citation Subset: IM; S |
Affiliation:
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Smith-Kettlewell Eye Research Institute, San Francisco, CA 94115, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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2-Amino-5-phosphonovalerate
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analogs & derivatives,
pharmacology Animals Curare / pharmacology Drug Combinations Excitatory Amino Acid Antagonists / pharmacology Motion Perception / drug effects, physiology* N-Methylaspartate / antagonists & inhibitors Nicotinic Antagonists / pharmacology Photic Stimulation / methods Rabbits Retina / physiology* Retinal Ganglion Cells / physiology Visual Pathways / physiology* Visual Perception / drug effects, physiology* |
| Grant Support | |
ID/Acronym/Agency:
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EY05070/EY/NEI NIH HHS; EY08921/EY/NEI NIH HHS; EY11170/EY/NEI NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Drug Combinations; 0/Excitatory Amino Acid Antagonists; 0/Nicotinic Antagonists; 6384-92-5/N-Methylaspartate; 76726-92-6/2-Amino-5-phosphonovalerate; 8063-06-7/Curare; 85797-13-3/2-amino-7-phosphonoheptanoic acid |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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