Changes of sleep patterns in rats with chronic constriction injury under aversive conditions

In the present study, we investigated the changes of sleep parameters in rats with chronic constriction injury (CCI) under aversive conditions. The electroencephalogram (EEG) in the frontal cortex of CCI rats and electromyogram (EMG) were measured over 6 h by placing rats on sandpaper as an aversive condition, to compare with rats placed on sawdust. Six days after CCI surgery, the rats exhibited significant mechanical allodynia, and also had neuropathic pain. When rats were placed on sawdust, no significant difference was observed between the CCI group and sham-operated control group in sleep latency, total waking time, total non-REM sleep time and total REM sleep time. On the other hand, when CCI rats were placed on sandpaper, a significant increase was observed in sleep latency and total waking time compared with the sham group; however, no significant difference was observed in the total non-REM sleep time and total REM sleep time between these two groups. These results indicate that an important factor of sleep disturbance in CCI rats is not only damage to the nerves but also being under aversive conditions. In addition, it was found that CCI rats placed on sandpaper as an aversive condition can serve as a new sleep disturbance model.