This MedLibrary.org supplementary page on Amacrine cells is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
| Amacrine cell | |
|---|---|
 |
|
| Location | INL of the retina |
| Function | inhibitory or neuromodulatory interneurons |
| Neurotransmitter | GABA, glycine, DA, or 5-HT |
| Morphology | Varies |
| Presynaptic connections | Bipolar cells |
| Postsynaptic connections | Bipolar cells and Ganglion cells |
Amacrine cells are interneurons in the retina. Amacrine cells are responsible for 70% of input to retinal ganglion cells. Bipolar cells, which are responsible for the other 30% of input to retinal ganglia, are regulated by amacrine cells.
Contents |
Overview
Amacrine cells operate at the inner plexiform layer (IPL), the second synaptic retinal layer where bipolar cells and retinal ganglion cells synapse. There are about 40 different types of amacrine cells, most lacking axons. Like horizontal cells, amacrine cells work laterally affecting the output from bipolar cells, however, their tasks are often more specialized. Each type of amacrine cell connects with a particular type of bipolar cell, and generally has a particular type of neurotransmitter. One such population, AII, 'piggybacks' rod bipolar cells onto the cone bipolar circuitry. It connects rod bipolar cell output with cone bipolar cell input, and from there the signal can travel to the respective ganglion cells.
They are classified by the width of their field of connection, which layer(s) of the stratum in the IPL they are in, and by neurotransmitter type. Most are inhibitory using either GABA or glycine as neurotransmitters.
Functionality
Relatively little is known of the functional roles of the Amacrine cells. Amacrine cells with extensive dendritic trees are thought to contribute to inhibitory surrounds by feedback at both the bipolar cell, and ganglion cell levels. In this role they are considered to supplement the action of the horizontal cells. Amacrine cells give much more input to M (Magnocellular) ganglion cells than to P (Parvocellular) ganglion cells.
Other forms of Amacrine cell are likely to play modulatory roles, allowing adjustment of sensitivity for photopic and scotopic vision. The AII Amacrine cell (also known as the Rod amacrine cell) is a mediator of signals from rod cells under scotopic conditions.
See also
References
- Nicholls, John G.; A. Robert Martin, Bruce G. Wallace, Paul A. Fuchs (2001). From Neuron to Brain. Boston, Massachusetts: Sinauer Associates, Inc. ISBN 0-87893-439-1.
- Masland RH (2001). "The fundamental plan of the retina". Nat. Neurosci. 4 (9): 877–86. doi:. PMID 11528418.
External links
- Webvision amacrine cell article
- MeSH A08.663.358.050
- Eye Brain and vision book Hubel D (1988) Eye Brain and Vision, whole book available online.
|
||||||||
Wikipedia content modification information:
- This page was last modified on 22 October 2008, at 03:23.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Amacrine cells".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.