Shedding light on circadian clock resetting by dark exposure: differential effects between diurnal and nocturnal rodents

Four-hour dark pulses led to phase advances in the circadian rhythm of locomotor activity in nocturnal and diurnal rodents.

• In Syrian hamsters, dark pulses shifted the circadian rhythm from subjective midday to dusk.
• In Arvicanthis ansorgei, dark pulses shifted the rhythm from subjective dusk to midnight.
• No resetting effect was observed during the middle of subjective night in hamsters but occurred during most of the subjective day in Arvicanthis.
• Phase advances in both species were associated with downregulation of clock genes Per1 and/or Per2 in the suprachiasmatic nuclei.
• Despite similar dark-induced phase advances, Per1 was downregulated in Arvicanthis but not in hamsters.

AI simplified