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. 2008 Nov 26;28(48):12956–12968. doi: 10.1523/JNEUROSCI.2890-08.2008

Figure 6.

Figure 6.

Unitary inhibitory postsynaptic conductance at BC output synapses becomes stronger and faster during postnatal development. A, Unitary IPSCs recorded in a pair of GFP-positive BCs in the young (P6; left) and the mature (P21; right) dentate gyrus. Presynaptic action potentials are shown on top, unitary IPSCs are shown superimposed in the center (6 traces), and average unitary IPSCs (from 30 traces) are depicted below. The decay phases of average IPSCs were fitted with a double-exponential function to determine the decay time constant (τw), and the quality of the fit is shown with gray superimposed lines. Arrows point to average IPSCs from a young (black) and a mature (orange) BC–BC paired recording. Traces were normalized to the peak amplitude and superimposed. Note that the decay time constant of unitary IPSCs is faster in the mature than in the young BC–BC pair. B, Summary plot of peak amplitudes (left) and amplitude-weighted decay time constants (τw; right) of unitary IPSCs recorded at BC–BC (filled circles) and BC–GC (open triangles) synapses at various postnatal ages (postsynaptic holding potential, −70 mV). Lines correspond to sigmoidal functions fitted to the data from BC–BC (continuous line) and BC–GC pairs (dashed line) for peak amplitudes (left) and exponential functions for τw (right). Red filled circles represent average values from BC–BC pairs, and red open triangles represent average values from BC–GC pairs in the age range of P6–P10 and of P18–P25. C, Connection probability between two BCs from 152 simultaneous recordings at P6–P25 (filled bars; P6–P8, 3 of 42 connected; P9–P11, 4 of 36 connected, P12–P17, 4 of 28 connected; P18–P25, 7 of 46 connected). Connection probability between presynaptic BCs and postsynaptic GCs from 148 paired recordings (open bars; P6–P8, 9 of 90 connected; P9–P11, 4 of 26 connected, P12–P17, 6 of 14 connected; P18–P25, 10 of 18 connected). D, Zolpidem (5 μm), a benzodiazepine type I receptor agonist, increases the decay time constant (τw) of IPSCs evoked by extracellular axon stimulation in mature but not in young BCs. **p < 0.01.