Does a Red House Affect Rhythms in Mice with a Corrupted Circadian System?

Area of Science:

• Chronobiology
• Neuroscience
• Animal Behavior

Background:

• Mammalian circadian rhythms are governed by the suprachiasmatic nucleus (SCN), which receives light input from the retina.
• Molecular clock genes form feedback loops driving rhythmic gene expression at the cellular level.
• Mice lacking the Bmal1 gene (Bmal1-/-) exhibit impaired circadian rhythms due to disrupted light input pathways.

Purpose of the Study:

• To investigate the impact of a red house (RH) on the behavior and physiology of Bmal1-/- mice.
• To determine if RH, a common animal welfare tool, affects circadian rhythms in mice with compromised circadian systems.

Main Methods:

• Assessed spontaneous locomotor activity in Bmal1-/- mice with and without RH.
• Evaluated mPER1 and p-ERK immunoreactions in the SCN as markers of neuronal activity.
• Measured day/night plasma corticosterone levels.

Main Results:

• The presence of RH abolished rhythmic locomotor behavior in Bmal1-/- mice.
• RH application dampened rhythmic SCN neuronal activity, indicated by reduced mPER1 and p-ERK immunoreactions.
• No significant effect of RH was observed on the day/night difference in corticosterone levels.

Conclusions:

• The red house (RH) disrupts established rhythmic behaviors and SCN neuronal activity in Bmal1-/- mice.
• Despite affecting behavior and SCN activity, RH does not alter the overall diurnal pattern of corticosterone levels in these mice.
• These findings highlight the complex interplay between environmental enrichment and circadian system integrity.