Deviant circadian rhythmicity, corticosterone variability and trait testosterone levels in aggressive mice

Area of Science:

• Neuroscience
• Chronobiology
• Behavioral Genetics

Background:

• Aggression is linked to circadian rhythm disturbances, but the underlying neural mechanisms are unclear.
• The suprachiasmatic nucleus (SCN), the master circadian clock, influences hormones like corticosterone and testosterone, which are implicated in aggression.

Purpose of the Study:

• To investigate circadian rhythm regulation and hormone levels in a mouse model of abnormal aggression.
• To explore the neural basis of the link between circadian function and aggressive behavior.

Main Methods:

• Comparison of locomotor circadian rhythms in aggressive (BALB/cJ) and control (BALB/cByJ) mice under light/dark and constant darkness conditions.
• Measurement of state (serum) and trait (hair) corticosterone and testosterone levels.
• Immunohistochemistry to assess clock protein (PER1, PER2) expression in the SCN.

Main Results:

• Aggressive mice exhibited a shorter free-running circadian period and reduced corticosterone variability.
• Lower testosterone levels and increased PER1 expression in the SCN shell were observed in aggressive mice.
• No significant differences in PER2 expression were found in either SCN subregion.

Conclusions:

• Aggressive mice display disruptions in circadian and hormonal regulation, involving the SCN and clock gene expression.
• These findings highlight the potential causal relationship between SCN function, circadian rhythms, and aggression.