Figure 1.
Assessment of direct OSN-EPSCs following electrical stimulation. ai, EPSCs recorded simultaneously from a same-glomerulus MC/ET cell pair in response to ON stimulation (20 μA). The ET cell, but not the MC, displayed a fast-occurring EPSC (arrowhead) distinct from a longer-lasting LLD. The diagonal arrows on expanded traces indicate estimated onset times for the EPSCs. All traces in figure are averages of 4–15 responses. aii, Images of the MC/ET cell pair from ai filled with Alexa 488 (100 μm). Labeled is the target glomerulus of the two cells (dashed ring), as well as glomerular (GL), external plexiform (EPL), and mitral cell (MCL) layers. b, EPSC evoked in an SMT cell by ON stimulation (13 μA). Like the ET cell in a, the SMT cell had a distinct rapid EPSC, in addition to a slow LLD. This cell had one prominent lateral dendrite (arrowhead on cell image). c, Summary of EPSC onset delays across all MCs (n = 16), ET cells (n = 13), SMT cells (n = 9), and DMT cells (n = 8), plotted as a cumulative histogram. Each data point reflects one cell. d, EPSC rise times (10–90%) across all recordings. e, Amplitudes of putative OSN-EPSCs across all recordings, estimated from the peak (Amp4 ms) measured during the first 4 ms after ON stimulation. f, A dendritic recording of the MC response to ON stimulation (100 μs, 27 μA; at white arrowhead on cell image) did not reveal a substantial fast OSN-EPSC. g, All cell types showed similar-sized LLDs (measured ≥30 ms after ON stimulation), also consistent with at most modest passive filtering effects by the trunk of the apical dendrites.