Purchase this article with an account.
Y. Xia, R.C. Carroll, S. Nawy; Visual Stimulation Modulates AMPA Receptor Trafficking and Synaptic Subunit Expression in Mammalian Retina . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1511.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
We have previously shown evidence that AMPA receptors (AMPARs) conditionally cycle into and out of the plasma membrane in mammalian retina, and the extent of cycling is inversely related with activity levels. More specifically, light stimulation modulates AMPARs cycling in a pathway specific manner. In light–adapted retina, the ongoing synaptic activity in ON cells serves to suppress AMPAR trafficking, whereas dark adaptation switches them into a cycling mode. However, the physiological relevance of this type of plasticity has not yet been examined; in particular, questions remain about the impact of cycling on synaptic transmission.
We did whole cell recording on cells in the ganglion cell layer. The AMPAR mediated light response and responses to puffs of AMPA were isolated with a cocktail solution of antagonists to GABA, glycine and NMDA receptors (Picrotoxin, Bicuculline, TPMPA, Strychnine and APV).
To investigate the timing requirement for inducing rapid trafficking in ON cells, we dark adapted mice for various periods of time and dialyzed cells with dynamin blocking peptide that is known to block endocytosis of AMPARs. We found that 8–hours of dark adaptation caused a 1.30±0.07 fold run–up of AMPA puff responses, suggesting that fast cycling of AMPARs can be induced within a normal day/night cycle. However, the amplitude of light response remained constant (1.01±0.06), indicating rapid AMPAR cycling occurs only within the extra–synaptic compartment. In separate experiments, we recorded synaptic light responses from ON cells dialyzed with spermine, which, at positive potentials blocks GluR2–lacking receptors, resulting in strong voltage–dependent rectification. In light adapted retina, light responses exhibited slight rectification (rectification ratio of 0.72±0.01), indicating that the synapses are composed predominantly of GluR2 containing receptors. Interestingly, we observed much stronger rectification in dark–adapted retina (rectification ratio of 0.32±0.03, p=0.01), implying cycling of AMPAR may remove GluR2–containing receptors away from synapses.
Our results suggest that during normal day/night cycle, light dynamically modulates extra–synaptic AMPAR trafficking between non–cycling and cycling modes. Perhaps independently or as a consequence of receptor cycling, light also changes the composition of synaptic AMPAR types and provides a mechanism of controlling synaptic transmission.
This PDF is available to Subscribers Only