Abstract

Daily rhythms are prominent in almost everything, from sleep/wake cycles, body temperature and hormone regulation to even cognition, motor coordination, attention and mood (McClung, 2007). Studies have shown that individuals with mood disorders and motor dysfunction exhibit alterations in the neural circuitry and neurochemistry in both the ventral and dorsal striatum (Del Donno et al., 2017) and recent research brought to the attention a potential involvement of the circadian system. There is evidence to suggest that the circadian clock gene Period2 may be implicated in the vulnerability and development of striatum-related illnesses ((Lamont et al., 2007; Kim et al., 2018). However, the majority of these findings present mixed results and the mechanisms through which the core clock gene may influence these behaviors is still not understood. Hence, our aim is to elucidate how a conditional knockout of Per2 in mood-and motor-related brain areas such as the striatum may contribute to circadian variation in striatum-related behaviors in male and female mice. Male and female mice of three representative genotypes: knockout (SKO), heterozygote (HET) and wild-type (WT), were used in a battery of behavioral tests to screen for striatum-related phenotypes. Animals were tested at two different time points (ZT2 or ZT14) for mood-related behaviors and ZT6 or ZT2 for motor function. Results indicated no differences in anxiety- and depressive-like behaviors across genotypes. However, SKO mice performed worse in the rotarod test in comparison to HET and WT mice, suggesting poorer motor coordination in mice where the circadian clock gene is conditionally knocked out from the striatum.