Fig. 2: Evoked corticostriatal glutamate transmission increases in VKI SPNs by 6 months.

A i) Schematic depicting ChR2 viral injection into motor cortex 4–6 weeks prior to preparation of acute coronal slices containing CTX and STR. Whole-cell patch-clamp recordings were obtained from dorsolateral striatal SPNs +/- NMDAR inhibitor, APV. ii) Representative ChR2-PSC traces in response to single pulses of light. SPNs that were held at membrane potentials of -70 mV or +40 mV (in black), and +40 mV in the presence of AP5 (in cyan). B At 3 months, i) the peak amplitude of AMPAR-mediated currents at -70 mV are not significantly different between WT and VKI SPNs (Unpaired t-test p = 0.46). ii) Amplitude of NMDAR-mediated currents are not significantly different between genotypes at +40 mV (Unpaired t-test p = 0.87). iii) Ratios of +40 mV NMDAR current to -70 mV AMPAR current are not significantly different between WT and VKI SPNs (Unpaired t-test p = 0.60). iv) Rectification Index of AMPA current is not significantly different between WT and VKI SPNs (Unpaired t-test p = 0.45). C At 6 months, i) VKI SPNs show larger currents than WT SPNs, in peak amplitude of both AMPAR-mediated current (Mann-Whitney U-test p = 0.01) and ii) NMDAR-mediated current (Unpaired t-test p = 0.0005). iii) Ratio of NMDA:AMPA currents are not significantly different between genotypes (Unpaired t-test p = 0.90). iv) AMPA Rectification Index is not significantly different between WT and VKI SPNs (Unpaired t-test p = 0.67). D i) Representative ChR2-PSCs with 4 pulses of ChR2 stimulation (in red), 100 ms inter-pulse interval. ii) At 3 months, the paired pulse ratio (PPR) of 4 responses to ChR2 stimulation, normalized to the first response, is not significantly different between VKI and WT SPNs (2-way ANOVA interaction p = 0.34, genotype p = 0.22). iii) At 6 months, the paired pulse ratio is significantly reduced in VKI vs WT SPNs (2-way ANOVA interaction p = 0.001, genotype p = 0.04).