Figure 6. Morphology and physiology of dentate gyrus granule cells in Ptchd1−/y mice. A, Diolistic labeling (red) of a hippocampal dentate granule cell (GC) in a P21 Ptchd1−/y (KO) mouse (DAPI labeling of nuclei in blue). The bottom panel shows an example of a P21 WT and KO DG granule cell distal dendrite. B, Spine density (per 30 μm dendrite segment) and morphology (headed vs nonheaded spines) were quantified for P21 and adult (P60) WT and Ptchd1−/y (KO) mice. Means of 4 WT and 4 Ptchd1−/y (P21) and 4 WT and 5 Ptchd1−/y (P60) mice are displayed (lines and solid dots); mean and unpaired Student's t test. The light dots represent values for individual dendritic segments scored (P21: Ptchd1−/y n = 44, WT n = 44; P60: Ptchd1−/y n = 49, WT n = 42). C, Schematic showing the configuration of whole-cell voltage-clamp recordings made from acute hippocampal slices of P21–P24 mice. Postsynaptic responses in GC neurons were measured after stimulation of the perforant pathway (pp). D, Representative traces of evoked EPSCs and IPSCs recorded from granule cells in acute hippocampal slices show disrupted excitation/inhibition balance in Ptchd1−/y (KO) granule cells (WT, n = 10; KO, n = 17; n = 3 animals for each genotype; mean ± SEM, unpaired t test). E, Representative traces of evoked EPSCs used to calculate AMPAR/NMDAR ratios (WT, n = 17; KO, n = 18; n = 3 animals for each genotype, unpaired t test). F, Normalized evoked postsynaptic responses of WT or Ptchd1−/y GC neurons to five stimuli delivered to the pp with a 50 interstimulus interval, The facilitation ratio of the second EPSC amplitude normalized to the first EPSC amplitude shows normal facilitation across various interstimulus intervals in Ptchd1−/y (KO) GC neurons (stimulus: third/first, p = 0.18; fourth/first, p = 0.43; fifth/first, p = 0.64; WT, n = 8; KO, n = 16; n = 3 animals for each genotype, two-way repeated-measures ANOVA with multiple comparisons). G, Representative traces of sEPSCs from WT or Ptchd1−/y GC neurons that were voltage clamped at −70 mV, sEPSC frequency (WT, 0.22 ± 0.04 Hz; KO, 0.39 ± 0.04 Hz), but not sEPSC amplitude (WT, 0.22 ± 0.04 Hz; KO, 0.39 ± 0.04 Hz), is increased in Ptchd1−/y GC neurons (WT, n = 10; KO, n = 16; n = 3 animals for each genotype, unpaired t test). H, Representative traces of sIPSCs from WT or Ptchd1−/y GC neurons that were voltage clamped at 0 mV. sIPSC frequency (WT, 0.53 ± 0.09 Hz; KO, 1.56 ± 0.3 Hz), but not sIPSC amplitudes (WT, 14.72 ± 0.67 pA; KO, 18.35 ± 1.57), is significantly increased in Ptchd1−/y GC neurons (WT, n = 10; KO, n = 15; n = 3 animals for each genotype, unpaired t test).