Amacrine cell

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.

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Overview

Amacrine cells operate at the inner plexiform layer (IPL), the second synaptic retinal layer where bipolar cells and 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

Functionally, they are responsible for complex processing of the retinal image, specifically adjusting image brightness and, by integrating sequential activation of neurons, detecting motion.

See also

• Photoreceptor cell
• Horizontal cell
• Bipolar cell
• Ganglion cell

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:10.1038/nn0901-877. PMID 11528418.