Figure 1. Intrinsic, morphological, and synaptic properties of non-FS and FS cells. A, Exemplar voltage responses evoked by a series of current pulses in a non-FS (blue) and an FS (red) cell. Current during the pulse was −0.1, 0.3, 0.6, and 0.8 nA. Membrane potential before the pulse was −70 mV. B, The relationship between the mean AP frequency and injected current for a subset of representative non-FS (n = 14) and FS (n = 16) cells. Individual cells were in lighter color, and the average values were darker. C, Summary of CV of ISI, τm, and Rin of non-FS (blue, n = 6–13) and FS (red, n = 7–17) cells. ***p < 0.0005. D, Exemplar reconstruction of a non-FS IN (D1), which had the main axonal distribution (blue) outside the GCL, and an FS IN (D2), which had the major axonal distribution (red) within the GCL. Somata and dendrites are indicated in black. ML, Molecular layer. E, Axonal density distribution for non-FS (n = 11) and FS (n = 4) INs plotted against distance from the GCL. A reconstructed GC (gray) is aligned and scaled to the plot for reference. F, Left, Schematic of paired recordings from a non-FS IN (blue)-to-GC (black) pair and a FS IN (red)-to-GC pair. Bursts of five APs were evoked in the non-FS IN and the FS IN by injection of brief current pulses (1 ms, 25 Hz) every 5 s. Presynaptic INs were current clamped at −70 mV, whereas postsynaptic GCs were voltage clamped at −80 mV. Right, The first AP from non-FS (blue) and FS (red) INs and their corresponding average uIPSCs (average of 70 and 73 sweeps, respectively, currents were inverted for clarity) in the target GCs (black) on an expanded time scale (vertical lines are separated by 2.5 ms). Squares represent average uIPSC latencies for non-FS (n = 11) and FS cells (n = 10). ***p < 0.0005. G, Summary of AP half-width (blue, n = 8; red, n = 10), 20–80% rise time (blue, n = 10; red, n = 12), and decay time constant (blue, n = 9; red, n = 12). ***p < 0.0005.