Fig. 4.
Excitatory synaptic input from bipolar cells to VGLUT3+ amacrine cells. (A) Glutamate release from presynaptic bipolar cells in the absence of inhibition (see Materials and methods section). Electrically evoked EPSCs (Vhold = −60 mV, inhibition blocked) were insensitive to TTX (1 µM, red trace) but were blocked by application of the AMPA-type receptor antagonist NBQX (10 µM, gray trace). (B) Scatter plot summarizing the drug effects for experiments in panel (A) (n = 6). (C) and (D) In the presence of NBQX (Vhold = +40 mV), a slower EPSC was blocked by the NMDAR antagonist RS-CPP (10 µM, gray trace). (D) EPSCs in the presence of NBQX exhibit a j-shaped current–voltage relationship characteristic of an NMDAR-mediated conductance.