Background
It has been known that skeletal muscles show atrophic changes after prolonged sedation or general anesthesia. Whether these effects are due to anesthesia itself or disuse during anesthesia has not been fully clarified. Autophagy dysregulation has been implicated in muscle-wasting conditions. This study tested the hypothesis that the magnitude of skeletal muscle autophagy is affected by both anesthesia and immobility.
Conclusions
Short-term disuse without anesthesia does not lead to autophagy, but anesthesia with disuse leads to marked up-regulation of autophagy.
Methods
The extent of autophagy was analyzed chronologically during general anesthesia. In vivo microscopy was performed using green fluorescent protein-tagged LC3 for the detection of autophagy using sternomastoid muscles of live mice during pentobarbital anesthesia (n = 6 and 7). Western blotting and histological analyses were also conducted on tibialis anterior muscles (n = 3 to 5). To distinguish the effect of anesthesia from that due to disuse, autophagy was compared between animals anesthetized with pentobarbital and those immobilized by short-term denervation without continuation of anesthesia. Conversely, tibialis anterior and sternomastoid muscles were electrically stimulated during anesthesia.
Results
Western blots and microscopy showed time-dependent autophagy up-regulation during pentobarbital anesthesia, peaking at 3 h (728.6 ± 93.5% of basal level, mean ± SE). Disuse by denervation without sustaining anesthesia did not lead to equivalent autophagy, suggesting that anesthesia is essential to cause autophagy. In contrast, contractile stimulation of the tibialis anterior and sternomastoid muscles significantly reduced the autophagy up-regulation during anesthesia (85% at 300 min). Ketamine, ketamine plus xylazine, isoflurane, and propofol also up-regulated autophagy. Conclusions: Short-term disuse without anesthesia does not lead to autophagy, but anesthesia with disuse leads to marked up-regulation of autophagy.