Effect of glycine on pain threshold and depressive-like behavior in sleep deprived mice

Objective To investigate the effect of glycine on pain threshold and depressive-like behavior in sleep-deprived mice through behavioral experiments. Methods A total of 40 mice were randomly divided into four groups (n=10): a control +normal saline (Control+NS) group, a control + glycine (Control+Gly) group, a sleep deprivation + normal saline (SD+NS) group, and a sleep deprivation + glycine (SD+Gly) group. A sleep deprivation model was established using the modified multiple platform method. The body weights of the mice in each group were measured. The pain thresholds of the mice in each group were determined by the hot plate test. Their depression-like behaviors were evaluated by the forced-swimming test. Results ①Compared with the Control+NS group, the SD+NS group showed significantly reduced body weight on days 3-5, while the SD + Gly group presented remarkable decreases body weight on days 3-4. ②Compared with the Control+NS group, the pain threshold of the Control+Gly group significantly increased on day 5, while that of the SD+NS group remarkably decreased on day 5. Compared with the SD + NS group, the SD+Gly group had obvious increases in pain threshold on day 5.③Compared with the Control+NS group, the percentages of floating immobility time to total time on day 5 significantly increased in the SD + NS group and the SD+Gly group. Compared with the SD + NS group, the percentage of floating immobility time to total time significantly decreased in the SD+Gly group on day 5. Conclusions Glycine can increase the pain threshold of sleep deprived mice and alleviate depressive-like behavior caused by sleep deprivation.