Restoration of sleep–wake behavior following short photoperiod exposure in ventral subicular lesioned male Wistar rats: A 24-h sleep–wake electroencephalographical study

The ventral subiculum regulates emotion, stress responses, and spatial and social cognition. In our previous studies, we have demonstrated anxiety- and depression-like symptoms, deficits in spatial and social cognition in ventral subicular lesioned (VSL) rats, and restoration of affective and cognitive behaviors following photoperiod manipulation (short photoperiod regime, SPR; 6:18 LD cycle). In the present study, we have studied the impact of VSL on sleep–wake behavioral patterns and the effect of SPR on sleep–wakefulness behavior. Adult male Wistar rats subjected to VSL demonstrated decreased wake duration and enhanced total sleep time due to increased non-rapid eye movement sleep (NREMS) and rapid eye movement sleep (REMS). Power spectral analysis indicated increased delta activity during NREMS and decreased sigma band power during all vigilance states. Light is one of the strongest entrainers of the circadian rhythm, and its manipulation may have various physiological and functional consequences. We investigated the effect of 21-day exposure to SPR on sleep–wakefulness (S–W) behavior in VSL rats. We observed that SPR exposure restored S–W behavior in VSL rats, resulting in an increase in wake duration and a significant increase in theta power during wake and REMS. This study highlights the crucial role of the ventral subiculum in maintaining normal sleep–wakefulness patterns and highlights the effectiveness of photoperiod manipulation as a non-pharmacological treatment for reversing sleep disturbances reported in mood and neuropsychiatric disorders like Alzheimer's disease, bipolar disorder, and major depressive disorder, which also involve alterations in circadian rhythm.