Table 1.

Rodent research in mood disorders using different light schedules.

Model	Animals used	Diurnal or Nocturnal	Circadian Rhythms, locomotor activity and/or sleep architecture	Behavioral responses observed	CORT levels	References
Constant light (LL)	Mice	Nocturnal	Most mice became arrhythmic, although some animals remained rhythmic with lengthened period or showed split locomotor activity rhythms.	Induces depression-like behaviors (SA and FST). Decreases anxiety-like responses (OFT and EPM). Impairs spatial memory (MWM)	↓	159–161
	Wistar rats	Nocturnal	Decrease amount of total time spent in NREMS (resting phase) and increase REMS episodes (active phase). Disruption of the pattern of circadian locomotor activity (it depends of the light intensity) and body temperature.	Induces anxiety (OFT and EPM). Impairs spatial memory (MWM).	NT	162
Constant dark (DD)	S-D rats	Nocturnal	The period remains close to 24-h but decreases the amplitude of the sleep-wake cycle (increases sleep in the active period).	Induces depression-like behaviors (FST).	NT	163
Dim Night-time Light exposition	Nile grass rats	Diurnal	No disruption of the pattern of circadian locomotor activity.	Induces depression-like behaviors (SA, FST, and Barnes maze).	↑	89
	Siberian hamsters	Nocturnal	Reduced dark-phase activity	Induces depression-like behaviors (SA and FST). Decreases anxiety-like responses (EPM).	↓	91, 164–166
	Mice	Nocturnal	No disruption of the pattern of circadian locomotor activity.	NT	=	159
Short daylight	Sand rats	Diurnal	NT	Induces depression-like behaviors (SA and FST). Induces anxiety disorders (EPM, but not in the OFT).	NT	61,62
	Nile grass rats	Diurnal	NT	Induces depression-like behaviors (SA and FST). No anxiety disorders (dark/light box) were observed.	NT	167
“Jet lag”	Golden hamsters	Nocturnal	Minor changes in the pattern of circadian locomotor activity (desynchrony between internal and external time).	Impairs spatial memory (conditioned place preference paradigm, used for hamsters).	↑	71
phase shift protocol	Siberian hamsters	Nocturnal	Permanently eliminate circadian rhythms, but preserves sleep architecture.	Deficits in spatial working memory and in long-term object recognition memory (spontaneous alternation test and NOR).	NT	106
	Long Evans rats / Albino rats	Nocturnal	NT	Impairs spatial memory (MWM). Produces retrograde amnesia (passive avoidance test)	NT	70,72
T7 cycle	Mice	Nocturnal	Normal amount of total sleep and REM sleep Not disruption of the pattern of circadian locomotor activity (desynchrony between internal and external time).	Induces depression-like behaviors (SA and FST). No anxiety disorders (dark/light box, OFT and EPM) were observed. Impairs spatial memory (NOR and MWM).	↑	52

SA: sucrose anhedonia; FST: forced swim test; OF: open field test; MWM: Morris water maze; NOR: nobel object; EPM: elevated plus-maze.

For cortiol levels, ↑ indicates increased levels, ↓ indicates decreased levels or blunted effect, = indicates that no differeces were found, and NT indicates that, at least to our knowledge, it has not been tested.