Supplementary Figure 5: Reduced frequency of Purkinje cell simple spike firing following neonatal hypoxia.

(a) Selected records illustrating representative Purkinje cell firing patterns. Each record is a 20 s segment from a longer cell-attached recording in voltage-clamp (at least 2 mins). The traces are from a Purkinje cell in a slice from a normoxic mouse (P11) and from two cells in slices from hypoxic mice (both P10). To the right are the corresponding inter-spike interval (ISI) histograms, together with the mean interspike interval (ISI), coefficient of variation of ISI (CV) and the coefficient of variation of adjacent intervals (CV2) and mean firing rate for the cells illustrated. As expected for Purkinje cells from young mice (P10-11), all cells in slices from normoxic mice exhibited a purely ‘tonic’ firing pattern. By contrast, ~30% of cells in slices from hypoxic mice displayed a ‘tonic-silent’ firing pattern, with periods of tonic firing interspersed by silent periods of ~1-10 s. None of the cells displayed a ‘trimodal’ (inactive/tonic/burst) pattern of firing. (b) Box-and-whisker plots showing the pooled data for mean firing rate and variability (n = 40 and 35 cells from 3 normoxic and 3 hypoxic mice, respectively). Box-and-whisker plots indicate the median value (black line), the mean (black cross), the 25-75th percentiles (box) and the 10-90th percentiles (whiskers). *** P < 0.001, Wilcoxon Mann-Whitney Rank Sum test. Frequency was reduced from 9.8 ± 0.7 Hz to 4.4 ± 0.6 Hz, Z = 5.50, P = 3.67e–9. ISI CV was increased from 0.12 ± 0.01 ms to 0.50 ± 0.08 ms, Z = −4.67, P = 1.03e–6. ISI CV2 was increased from 0.12 ± 0.01 ms to 0.29 ± 0.04 ms Z = −3.70, P = 0.00021. (c) Scatter plot (log axes) of firing rate against ISI CV, illustrating the varied effect of hypoxia; a subset cells exhibited properties similar to those recorded from normoxic mice while a majority of cells (23/35) had lower firing rates and increased CV.