A1 adenosine receptor activation is not necessary for depolarization-induced presynaptic silencing. A, Example action-potential-evoked EPSCs from autaptic neurons treated 4 h with 30 mM NaCl (baseline) or 30 mM KCl (depolarized) in the presence or absence of 200 nM DPCPX, an A1 receptor antagonist. B, Summary of EPSC amplitudes from autaptic neurons treated as in A (n = 9 neurons). All comparisons were significantly different ( p < 0.05 with Bonferroni’s correction for multiple comparisons) except those indicated (N.S.). C, Example images of vGluT-1 (red) and FM1-43FX (green) correspondence in neurons treated 4 h under baseline or depolarized conditions in the presence or absence of 200 nM DPCPX. Scale bar, 5 μm. D, Summary of conditions represented in C (n = 65 fields from 13 independent experiments). All comparisons were significantly different ( p < 0.05 with Bonferroni’s correction for multiple comparisons) except those indicated (N.S.).