Synaptic Pharmacology of Ganglion Cell Hyperactivity

Pre- & postsynaptic origins of spontaneous hyperactivity
Retinal ganglion cells (RGCs) of degenerate retinas fire spontaneous action potentials at unusually high rates.  Pharmacologic blockade of known synaptic transmitters in the retina eliminates this activity in ~70-80% of RGCs, indicating that it is transmitted from other retinal cells presynaptic to the RGCs (e.g., bipolar or amacrine cells).  What about the remaining 20-30%?  Preliminary data suggests modulation of the activity by dopamine and/or gap junctions.