Photic Entrainment Is Altered in the 5-HT1B Receptor Knockout Mouse

Wild-type mice entrained to T = 21 h and T = 22 h cycles, while 5-HT1B receptor knockout (5-HT1B KO) mice did not.

• 5-HT1B KO mice were able to entrain to T = 23 h and T = 26 h cycles but showed altered phase angles compared to wild-type mice.
• Under T = 23 h conditions, 5-HT1B KO mice were significantly more phase delayed, while under T = 26 h conditions, they were significantly more phase advanced than wild-type mice.
• In a short-day photoperiod (9.5L:13.5D), the delayed phase angle of entrainment in 5-HT1B KO mice was more pronounced.
• Light-induced phase shifts were reduced in 5-HT1B KO mice, indicating an attenuated response to light.
• The altered entrainment in 5-HT1B KO mice may provide insights into circadian rhythm disruptions associated with seasonal affective disorder.

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