Effects of general anesthesia on behavioral circadian rhythms and clock-gene expression in the suprachiasmatic nucleus in rats

The suprachiasmatic nucleus (SCN) of the hypothalamus is a nucleus that regulates circadian rhythms through the cyclic expression of clock genes. It has been suggested that circadian-rhythm-related, adverse postoperative events, including sleep disturbances and delirium, are partly caused by anesthesia-induced disruption of clock-gene expression. We examined the effects of multiple general anesthetics on the expression cycle of Period2 (Per2), one of the clock genes that regulate circadian rhythms in the SCN, and on the behavioral rhythms of animals. Rats were treated with sevoflurane, propofol, and dexmedetomidine for 4 h. The expression of Per2 in SCN was analyzed using in situ hybridization, and the behavioral rhythm before and after anesthesia was analyzed. Per2 expression in the SCN decreased significantly immediately after anesthesia in all groups compared with corresponding control groups. However, Per2 returned to normal levels within 24 h, and there was no phase change in the gene expression cycle or behavioral rhythm. This study suggests that acute suppression of Per2 expression may be a general phenomenon induced by general anesthesia, but that the molecular mechanism of the body clock is resilient to disturbances to some extent.