Figure 6. Aberrant presynaptic calcium signalling in Xrcc1^−/− hippocampal neurons is rescued by Parp1 deletion or inhibition.

• A
  Representative image of DIV15 dissociated cultured neurons used. Scale bar: 100 µm.
• B
  (Top) Cartoon schematic illustrates SyGCaMP6f targeting and action. (Bottom) Image shows typical punctate SyGCaMP6f expression at DIV15. Scale bar, 20 µm.
• C
  Representative images of fluorescence responses in synaptic terminals expressing SyGCaMP6f to a train of 10 stimuli at 10 Hz in dissociated hippocampal neurons derived from wild‐type and mutant mice. Scale bar: 5 µm.
• D, E
  Mean SyGCaMP6f responses to three rounds of 10 action potentials stimulation from mice of the following genotypes: WT (n = 1,946 synapses, nine coverslips, three animals), Xrcc1^Nes‐Cre (n = 3,313, 12, 4), Parp1^+/−/Xrcc1^Nes‐Cre (n = 2,272, 9, 3) and Parp1^−/−/Xrcc1^Nes‐Cre (n = 2,122, 11, 3).
• F
  Response to chronic treatment with the PARP inhibitor, KU 0058948 Hydrochloride (1 µM) for 9–11 days prior to imaging for Xrcc1^+/+ (n = 1,264 synapses, eight coverslips, three animals) and Xrcc1^Nes‐Cre (n = 2,231, 10, 4) mice.
• G
  Summary histogram of the mean (± SEM) of the integrated fluorescence responses for all individual synapses for each condition. Synapse number is the same as in (D–F). Responses are significantly higher in Xrcc1^Nes‐Cre synapses versus both WT and Parp1^−/−/Xrcc1^Nes‐Cre (one‐way ANOVA, *P < 0.0033 and pairwise Student’s t‐tests).

Data information: (D–F) Data are from three or more independent experiments per genotype/treatment type, combined into one experimental data set and plotted on three separate graphs for clarity. Dashed lines in panels E and F are the WT and/or Xrcc1^Nes‐Cre curves transposed from panel D for comparative purposes.