Figure 5. Elevated Drd1 Signaling Reduces Neuronal Firing Rate in the SCN.

(A) Representative double-plotted actogram of wheel running activity in constant darkness (DD). White and grey background indicates the light and dark phase of the LD cycle, respectively.

(B) Average daily activity onset time. Repeated-measures three-way ANOVA with Bonferroni post-hoc comparison, n=7–10/group; F_genotype(1,28)=11.7, p=0.002, F_diet(1,28)=15.5, p<0.001.

(C) Average DD free running period (Tau). Two-way ANOVA with Bonferroni post-hoc comparison, n=6–9/group; F_genotype(1,27)=16.2, p<0.001, F_diet(1,27)=14.01, p<0.001.

(D) Quantification of dopamine turnover (DOPAC/DA ratio) following one-hour SCD or HFD exposure in hypothalamic tissue punches containing the SCN. Student’s two-tailed t-test, n=7/group.

(E) Mean firing rate of cell attached SCN neuron recordings following SKF-81297 (5μM) incubation at ZT8–11 (Day) or ZT14–17 (Night). Two-way ANOVA, n=13–26/group; F_time(1,70)=16.9, p<0.001, F_treatment(1,70)=6.8, p=0.01.

(F) Schematic of bilateral AAV2-DIO-ChR2-YFP injection in the SCN of Drd1^cre/+ mice.

(G) Representative traces from whole-cell current-clamp recordings. SCN neurons exhibit both depolarizing (top) and hyperpolarizing (bottom) responses to 20 Hz stimulation.

(H) ChR2 stimulation-induced average peak responses for depolarizing (Depol.), hyperpolarizing (Hyper.) and non-responsive (None) neurons. Distribution of recorded responses are depicted. (B.) indicates one cell exhibiting both responses (see Figure S5H).

(I) Response latency of each group in (H). Student’s two-tailed t-test, n=11/group.

(J) Representative traces from whole-cell current-clamp recordings for ChR2 stimulation-induced postsynaptic responses before and after 5 min 100μM PTX incubation.

(K) ChR2 stimulation-induced average peak responses before and after PTX incubation. Student’s two-tailed paired t-test, n=5/group.

Data are represented as mean±SEM. *p<0.05,**p<0.01,***p<0.001.

See also Figure S5.