Direct and specific effect of sevoflurane anesthesia on rat Per2 expression in the suprachiasmatic nucleus.

BACKGROUND: Our previous studies revealed that application of the inhalation anesthetic, sevoflurane, reversibly repressed the expression of Per2 in the mouse suprachiasmatic nucleus (SCN). We aimed to examine whether sevoflurane directly affects the SCN. METHODS: We performed in vivo and in vitro experiments to investigate rat Per2 expression under sevoflurane-treatment. The in vivo effects of sevoflurane on rPer2 expression were examined by quantitative in situ hybridization with a radioactively-labeled cRNA probe. Additionally, we examined the effect of sevoflurane anesthesia on rest/activity rhythms in the rat. In the in vitro experiments, we applied sevoflurane to SCN explant cultures from Per2-dLuc transgenic rats, and monitored luciferase bioluminescence, representing Per2 promoter activity. Bioluminescence from two peripheral organs, the kidney cortex and the anterior pituitary gland, were also analyzed. RESULTS: Application of sevoflurane in rats significantly suppressed Per2 expression in the SCN compared with untreated animals. We observed no sevoflurane-induced phase-shift in the rest/activity rhythms. In the in vitro experiments, the intermittent application of sevoflurane repressed the increase of Per2-dLuc luminescence and led to a phase delay in the Per2-dLuc luminescence rhythm. Sevoflurane treatment did not suppress bioluminescence in the kidney cortex or the anterior pituitary gland. CONCLUSION: The suppression of Per2-dLuc luminescence by sevoflurane in in vitro SCN cultures isolated from peripheral inputs and other nuclei suggest a direct action of sevoflurane on the SCN itself. That sevoflurane has no such effect on peripheral organs suggests that this action might be mediated through a neuron-specific cellular mechanism or a regulation of the signal transduction between neurons.

Time-dependent repression of mPer2 expression in the suprachiasmatic nucleus by inhalation anesthesia with sevoflurane.

Some anesthetics can affect gene expression. Previously, we reported that sevoflurane anesthesia drastically and reversibly repressed the expression of mouse Per2 (mPer2), a core clock gene in the suprachiasmatic nucleus (SCN). In the current study, we examined the time-dependent effect of sevoflurane on mPer2 expression and its interactions with the circadian rest/activity rhythm of mice. During certain hours of the day, mice were anesthetized with 2.5% sevoflurane in 40% oxygen for 4h. The expression level of mPer2 in the SCN was measured by in situ hybridization using a radiolabeled cRNA probe. Anesthesia during the morning hours showed the greatest repressive effect on mPer2 expression. Sevoflurane anesthesia repressed mPer2 expression during the conditions of light/dark and constant dark, and the light conditions modified the repression rate under anesthesia. Moreover, anesthesia in the morning also repressed mPer2 expression the following day. This dominant effect of anesthesia in the morning indicates that sevoflurane anesthesia affects the onset of mPer2 transcription. Behavior analysis revealed that the anesthetic treatment also induced a phase-delay in the rest/activity rhythm. However, no time-dependent effects of anesthesia on the circadian rest/activity rhythm were observed. Further investigation into the molecular events caused by anesthesia are required to explain atypical clinical signs observed in patients after surgical procedures, such as fatigue, sleep disorder, mood alteration and delirium.

The general anesthetic sevoflurane affects the expression of clock gene mPer2 accompanying the change of NAD+ level in the suprachiasmatic nucleus of mice.

Sevoflurane is an anesthetic for the general anesthesia. In this study, we showed that sevoflurane anesthesia affects the expression of mouse Per2 (mPer2), which is a clock gene in the brain which is considered the organ where the anesthetics act in. 64.5% of mPer2 circadian expression was repressed under anesthesia in the suprachiasmatic nucleus (SCN) of the brain. After recovering from the anesthesia, the repressed mPer2 expression was restored to the same level as in non anesthesia-treated mice. This repression pattern was also observed in the subsequent phases of diurnal mPer2 expression. However, obvious phase-shift in the mPer2 expression was not showed in this study. On the other hand, the behavior analysis in this experiment exhibited that the phases in the circadian behavioral rhythm were shifted backwards. We also measured the NAD(+) level in the SCN, which was a mediator regulating the mPer2 expression. Then, significant increase of NAD(+) was detected under the anesthesia. These results indicate that the anesthesia induces the increase of NAD(+), and consequently leads to the repression of mPer2 expression and modifies the circadian expression pattern and diurnal behavioral rhythm of mice. Furthermore, the modification of mPer2 expression by the anesthesia is considered to affect various gene expressions.