Figure 5.

Decreasing the firing rate of dopaminergic cells leads to decreased ‘risk taking' behavior in ClockΔ19 mice. (a) Herpes simplex virus (HSV)-injected ClockΔ19 and wild-type (WT) mice were subjected to a dark/light test and the time spent on the light side was measured. HSV-Kir2.1-injected mutant mice spent less time in the light side as compared with HSV-green fluorescent protein-injected mice. Wild-type HSV-Kir2.1-injected mice spent significantly more time in the light side than WT HSV-GFP-injected mice (n=9–15, ^*P&lt0.05 by analysis of variance (ANOVA)). There is a significant difference in time spent in the lighted area between wild-type and ClockΔ19 mice injected with HSV-GFP (P<0.05). (b) HSV-injected ClockΔ19 and WT mice were subjected to the elevated plus-maze test. The time spent on the open arms was determined by video tracking software. HSV-Kir2.1-injected mutant mice spent significantly less time in the open arm as compared with HSV-GFP-injected mice (n=10–20, ^*P<0.05 by ANOVA). There is a significant difference in time spent on the open arm in between wild-type and ClockΔ19 mice injected with HSV-GFP (P<0.001).