Figure 4.

A, IR-DIC image of two MSNs (from an R6/2 mouse) that were bidirectionally connected. B, Depolarization-induced action potentials in MSN 1 evoked time-locked PSPs in MSN 2. C, Depolarization-induced action potentials in MSN 2 evoked PSPs in MSN 1. Traces on the right are the enlarged area in the dashed box. Asterisks show the three evoked PSPs. D, There was a reduced proportion of connected pairs in R6/2 MSNs compared with WTs (31/66 vs 11/67 in WT vs R6/2; χ² test, p < 0.001). E, Success rates, although slightly increased in R6/2 MSNs compared with those from WTs, were not significantly different. F, At each age there was a significant decrease in the proportion of connected pairs in MSNs from R6/2s compared with WTs. BD indicates that bidirectional connected pairs were present 50% of the time in MSNs, but only in R6/2 mice. G, Success rates were similar in MSNs from WT and R6/2 mice at the <30 and >60 d groups but were increased in MSNs from R6/2 mice between 30 and 60 d. These differences were not statistically significant. H–K, The PSP amplitudes and areas were significantly smaller in MSNs from R6/2 mice. PSP rise time was significantly slower and decay times were similar.