Age-dependent axonal dysfunctions and altered sharp-wave ripple oscillations in Scn1a+/− mice

Figures

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  Figure 1. Age-dependent differences in ripple oscillation frequencies between WT and Scn1a+/− mice (A) Example traces show spontaneous SPW-R activity. Field potentials were recorded in the pyramidal cell layer of hippocampal area CA1. Data were collected from slices obtained from either juvenile WT (green trace, top) or Scn1a+/− mice (magenta trace, bottom). (B) Example traces for SPWs with superimposed ripple oscillations at an expanded timescale (left) and respective band-pass (BP) filtered signals within a frequency range of 150–300 Hz (right). (C) Summary plot for sharp wave amplitudes (left), frequencies of SPW (middle), and ripple oscillation frequencies (right). (D) Example traces from slices obtained from either young adult WT (black trace, top) or Scn1a+/− mice (orange trace, bottom). (E) Example traces for SPWs with superimposed ripple oscillations at an expanded timescale (left) and respective band-pass (BP) filtered signals within a frequency range of 150–300 Hz (right). (F) Summary plot for sharp wave amplitudes (left), frequencies of SPW (middle), and ripple oscillation frequencies (right). For (C), summary data from n = 9 WT and n = 14 Scn1a+/− mice aged P19-22. For (F),…

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  Figure 2. Weaker coupling of IPSCs in CA1 pyramidal cells to local ripple oscillations in slices from young adult Scn1a+/− mice (A) Representative traces of field (upper traces) and whole-cell voltage clamp (0 mV holding potential) recordings (lower traces) from slices from a juvenile WT (green, left) and Scn1a+/− (magenta, right) mouse showing SPW-evoked IPSC trains. (B) Summary graphs of normalized SPW-evoked charge values calculated from IPSC trains in pyramidal cells representing the median area under the curve of IPSC trains divided by the respective median SPW amplitude. (C) Mean distributions of normalized event cross-correlations calculated for delays between IPSCs to ripple troughs per SPW-R. (D) Summary graphs for coupling and coupling precision quantifying the central peaks in individual event cross correlations. (E) Representative traces of field (upper traces) and whole-cell voltage clamp (0 mV holding potential) recordings (lower traces) from slices from a young adult WT (black, left) and Scn1a+/− (orange, right) mouse showing SPW-evoked IPSC trains. (F) Summary graphs of normalized SPW-evoked charge values calculated from IPSC trains in pyramidal cells representing the…

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  Figure 3. Differential AP coupling to ripple oscillations in PV-INs of WT and Scn1a+/− mice (A) Representative traces of field potential (upper traces) and whole-cell current-clamp recordings (lower traces) from slices prepared from either juvenile WT (green, left) or Scn1a+/− (magenta, right) mice showing SPW-R-evoked APs. (B) Mean distribution of normalized event cross-correlations calculated between detected APs and ripple troughs for each SPW-R per mouse for both groups. (C) Summary plot for the number of APs per SPW-R normalized for SPW amplitude. (D) Summary plot for the maximum bin count for AP-to-ripple delays in the respective histogram for each recording. (E) The width (sharpness) of the central peak of the respective histogram for each recording representing coupling precision. (F) Representative traces from slices from either young adult WT (black, left) or Scn1a+/− (orange, right) mice showing SPW-R-evoked APs. (G) Mean distribution of normalized event cross-correlations calculated between detected APs and ripple troughs for each SPW-R per mouse for both groups. (H) Summary plot for the number of APs per SPW-R divided by SPW amplitude. (I) Summary plot for the maximum bin…

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  Figure 4. Weaker coupling of IPSCs in CA1 PV-INs to local ripple oscillations in slices from young adult Scn1a+/− mice (A) Representative traces of field (upper traces) and whole-cell voltage clamp (0 mV holding potential) recordings (lower traces) from slices from a juvenile WT (green, left) and Scn1a+/− (magenta, right) mouse showing SPW-R-evoked IPSC trains. (B) Summary graphs of normalized SPW-R-evoked charge values calculated from IPSC trains in PV-INs representing the median area under the curve of IPSC trains divided by the respective median SPW amplitude. (C) Mean distributions of normalized event cross-correlations calculated for delays between IPSCs to ripple troughs per SPW-R. (D) Summary graphs for coupling and coupling precision quantifying the central peaks in individual event cross correlations. (E) Representative traces of field (upper traces) and whole-cell voltage clamp (0 mV holding potential) recordings (lower traces) from slices from a young adult WT (black, left) and Scn1a+/− (orange, right) mouse showing SPW-R-evoked IPSC trains. (F) Summary graphs of normalized SPW-R-evoked charge values calculated from IPSC trains in pyramidal cells representing the median area…

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  Figure 5. APs during SPW-R show age-dependent deficits in PV-IN from Scn1a+/− mice (A) Spontaneous SPW-R field activity and SPW-R-evoked AP firing in slices from juvenile WT (green traces) and Scn1a+/− (magenta traces) mice. (B) Overlay of SPW-R-evoked APs recorded from either a PV-IN from a juvenile WT mouse or a Scn1a+/− mouse. (C–F) Summary plots for AP amplitude, AP rising slope, AP width, and AP threshold. (G) Spontaneous SPW-R field activity and SPW-R-evoked AP firing in slices from young adult WT (black traces) and Scn1a+/− (orange traces) mice. (H) Overlay of SPW-R-evoked APs recorded from either a PV-IN from a young adult WT mouse or a Scn1a+/− mouse. (I–L) Summary plots for AP amplitude, AP rising slope, AP width, and AP threshold. For (C–F), summary data from n = 15 WT mice, n = 11 Scn1a+/− mice aged P19-22. For (I–L), summary data from n = 8 WT mice, n = 12 Scn1a+/− mice aged P30-37. ns = p > 0.05, ∗ = p < 0.05, ∗∗ = p < 0.01, ∗∗∗ = p < 0.001, Welch’s t test. Data are represented as mean ± SEM. See also Figure S4 and Table S1.

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  Figure 6. A low dose of TTX induces differential effects in young adult WT vs. Scn1a+/− mice (A) Overlay of current-evoked AP trains (inset, left) and the first 50 ms of the trains (right) recorded in a PV-IN from a juvenile WT mouse in control conditions (green trace) and after 20 min in 4 nM TTX (blue trace). (B) Similar to (A), but an overlay of data from a juvenile Scn1a+/− mouse. (C) Mean ± SEM of normalized amplitudes of the 5th APs for juvenile WT and Scn1a+/− mice during application of 4 nM TTX. (D) Relative TTX-induced changes in AP amplitude, AP rising slope, and AP width after 20 min of 4 nM TTX bath application. (E) Overlay of AP trains recorded in a PV-IN from a young adult WT mouse in control conditions (black trace) and after 20 min in 4 nM TTX (blue trace). (F) Similar to (E), but an overlay of data from a young adult Scn1a+/− mouse. (G) Mean ± SEM of normalized amplitudes of the 5th APs for young adult WT and Scn1a+/− mice during the application of 4 nM TTX. (H) Relative TTX-induced changes in AP amplitude, AP rising slope, and AP width after 20 min of 4 nM TTX bath application. For (C and D), summary data from n = 6 WT mice, n = 5 Scn1a+/− mice aged P20-22. For (G and H),…

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  Figure 7. Axonal recordings from PV-INs confirm an age-dependent AP deficit (A) Illustration of whole-cell current clamp recordings from the proximal axon of PV-INs. Left, combined two-photon image of tdTomato and Alexa 488 identifying the patched PV-IN in stratum pyramidale (s. pyr.). Right, individual imaging channels at higher magnification. Recording pipettes are added for illustrative purposes only. Scale bars represent 20 μm. s. rad., stratum radiatum; s. oriens, stratum oriens. (B) Overlay of axonal APs induced by somatic current injection to either a PV-IN from a juvenile WT (green trace) or Scn1a+/− mouse (magenta trace). (C) Summary plots for AP amplitude, AP rising slope, and AP width for juvenile WT and Scn1a+/− mice. (D) Overlay of axonal APs induced by somatic current injection to either a PV-IN from a young adult WT (black trace) or Scn1a+/− mouse (orange trace). (E) Summary plots for AP amplitude, AP rising slope, and AP width for young adult WT and Scn1a+/− mice. For (C), summary data from n = 6 WT mice, n = 10 Scn1a+/− mice aged P19-23. For (E), summary data from n = 10 WT mice, n = 7 Scn1a+/− mice aged P30-34. ns = p > 0.05, ∗ = p < 0.05, Mann-Whitney U test. Data are…