Degeneration and RepairDoes circadian rhythm disruption during their early development have lasting effects on cognition of the elder rats?Zhang, Yugea,,b,,c,,d; Wang, Wenzhub,,c,,e; Li, Yia; Shen, Jiayia; Zhang, Tonga,,b,,c,,dAuthor Information aSchool of Rehabilitation, Capital Medical University bBeijing Institute for Brain Disorders Neural Injury and Repair Centre cBeijing Key Laboratory of Neural Injury and Rehabilitation dNeural Rehabilitation Centre, Beijing Boai Hospital, China Rehabilitation Research Center eChinese Institute of Rehabilitation Science, Beijing, China Received 4 February 2020 Accepted 1 March 2020 Correspondence to Dr. Tong Zhang, Neural Rehabilitation Centre, Beijing Boai Hospital, China Rehabilitation Research Center, No.10, Jiao Men Bei Road, Fengtai District, Beijing 100068, China, Tel: +86 13701395491; e-mail: email@example.com NeuroReport: May 7, 2020 - Volume 31 - Issue 7 - p 544-550 doi: 10.1097/WNR.0000000000001443 Buy Metrics Abstract Objectives This study aimed to investigate the changes in learning and memory after chronic circadian disruption followed by a long period of circadian recovery. Materials and methods Eleven adult male spontaneously hypertensive rats were randomly divided into control group, 12-h light/12-h dark circadian disruption group (12L/12D) and 6-h light/6-h dark circadian disruption group (6L/6D). Rats in control group remained under the original 12-h light/12-h dark cycle throughout the experiment; rats in the 12L/12D group were exposed to 12-h light/12-h dark cycle with light–dark order changed every 3 days; rats in the 6L/6D group were exposed to 6-h light/6-h dark cycle. The disruption period continued for 18 weeks. Then after 8 weeks and 32 weeks of circadian re-entrainment, all animals were tested by Morris Water Maze (MWM), respectively, followed by an MRI examination. Results Rats in the 12L/12D group demonstrated longer escape latency and swim distance in the MWM test than rats in the other two groups (P < 0.05). The MRI results showed volume% reduction and concentration% decrease of brain regions in the two circadian disruptive groups, while the changes were more significant and comprehensive in the 12L/12D group (P < 0.05). Conclusions Circadian disruption during early life accelerates cognition decline in later life in rats. Frequent light–dark order shift is more harmful. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.