Time-of-Day-Dependent Effects of Rehabilitation on Motor Recovery After Experimental Focal Cerebral Ischemia

Rehabilitation is an efficacious method to improve poststroke motor dysfunction. Various rehabilitative techniques have become popular in this field of research. However, it has not been reported whether better outcomes can be achieved if rehabilitation training is conducted at the optimal time of the day.

A model of photothrombotic ischemic stroke was used in C57BL/6 mice, and poststroke 24-hour activity cycles were evaluated. We found an activity peak around Zeitgeber time (ZT)13 (21:00) and a trough around ZT20 (04:00) during the dark phase. In addition, we selected ZT6 (14:00) as the daytime training group (corresponding to the ZT13 training group, ZT20 training group, and ZT6 training group, respectively). The 3 groups underwent treadmill training for 4 weeks. Functional and histological recovery levels were compared. In addition, bulk RNA sequencing analysis was used to explore the possible molecular mechanisms.

The results showed that stroke-induced mice maintained a regular nocturnal locomotor rhythm with reduced amplitude. Motor recovery was greater in the ZT13 training group than in the ZT6 group, with a trend toward better outcomes at ZT13 than ZT20. The ZT13 group also showed superior neuronal survival and neurogenesis compared with ZT6, while improvements between ZT13 and ZT20 were less pronounced. Bulk RNA sequencing suggested that synaptic plasticity, calcium signaling, cAMP signaling, and MAPK (mitogen-activated protein kinase) signaling pathways contributed to neural repair differences between ZT13 and ZT6. In addition, the results showed a similar pattern of motor recovery in female and aged mice trained at ZT13 compared with ZT6, reinforcing the benefits of time-of-day training.

In conclusion, rehabilitative training during the most active phase is beneficial for enhanced recovery outcomes. Our study suggests that rehabilitation should be conducted when the body is in an optimal physiological state-that is, a time-of-day-dependent rehabilitation strategy.