Abstract
Purpose: :
Examine the role of D–serine as a coagonist for NMDA receptors in ganglion cells in the rabbit retina.
Methods: :
We recorded extracellular impulse activity from ganglion cells in the rabbit retina using an everted, superfused retina–eyecup preparation. Pharmacological manipulations were carried out by adding agents to the bathing medium while monitoring the light responses using peristimulus time histograms and ratemeter records. We examined the effects of D–serine and other glutamate receptor ligands on several different types of retinal ganglion cells.
Results: :
When D–serine was added to the bathing medium, we observed mixed effects on the impulse activity of ganglion cells. However, by using NBQX, a selective AMPA receptor antagonist, we restricted the light–evoked responses to those dominated by NMDA receptors. When D–AP7 was added to the NBQX bathing medium, light responses were typically eliminated, though a few exceptions were observed. In the presence of NBQX, the addition of D–serine commonly enhanced the light–evoked responses, and this effect reversed upon returning to the NBQX environment.
Conclusions: :
The results of this study demonstrate that the coagonist sites of NMDA receptors of the rabbit retina are not saturated under the conditions of our experiments. This explains why D–serine modulated the light–evoked responses dominated by NMDA receptor activity. These observations are consistent with the idea that D–serine plays a role as an NMDA receptor coagonist in the rabbit retina.
Keywords: retina: proximal (bipolar, amacrine, and ganglion cells) • retinal glia • synapse