Activity-dependent synaptic plasticity in retinal ganglion cells.

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Retinal Circuitry

Background:

• AMPA-type receptors (AMPARs) undergo rapid cycling via endocytosis and exocytosis at excitatory synapses, a process implicated in synaptic plasticity.
• While AMPAR cycling's role in synaptic function is unclear, it occurs in retinal neurons and is inhibited by synaptic activity.

Purpose of the Study:

• To investigate the subunit specificity and localization of AMPAR cycling.
• To elucidate the plasticity mechanisms at the ON bipolar cell-ON ganglion cell synapse.
• To link AMPAR cycling and synaptic receptor composition in response to visual stimuli.

Main Methods:

• Recordings from cultured retinal neurons and ON ganglion cells.
• Analysis of AMPAR subunit composition (GluR2-containing vs. GluR2-lacking).
• Investigation of AMPAR cycling disruption and its effect on synaptic receptor numbers.

Main Results:

• Rapid AMPAR cycling is mainly restricted to GluR2-containing receptors and occurs at extrasynaptic sites.
• Synaptic quiescence induces a shift in ON bipolar cell-ON ganglion cell synapses from GluR2-containing to GluR2-lacking AMPARs.
• Disrupting AMPAR cycling increases GluR2-containing receptors at the ON bipolar cell-ON ganglion cell synapse.

Conclusions:

• AMPAR cycling regulates the surface and synaptic pool of GluR2-containing receptors.
• Synaptic activity cessation allows GluR2-containing AMPARs to reach synapses, altering synaptic composition.
• Ambient light, via modulation of AMPAR cycling, can influence ON ganglion cell synaptic receptor composition.