Association between the Activation of Melanin‐concentrating Hormone (MCH) Producing Neurons and REM Sleep in Rats

Introduction Rapid eye movement sleep (REMS) rebound after REMS deprivation is characterized by increased time spent in REMS and the activation of melanin‐concentrating hormone (MCH) expressing neurons of the hypothalamus, known to have a central role in REMS regulation. The time spent in REMS shows strong correlation with activation of MCH cells of the hypothalamus. Materials and Methods Male Wistar rats were selectively REMS deprived (72h, flower‐pot method), followed by a 3h rebound sleep, during which EEG, EMG and motility were recorded. Immediately after rebound, each animal was perfused. MCH/cFos immunohistochemistry (cFos as an indicator of neuronal activation) was performed on hypothalamic setions. Home cage animals were used as controls. Data were evaluated by Spearman‐correlation. Results During REMS rebound, both the number of REMS episodes and the average duration of REMS items increased. However, a positive correlation with MCH/cFos double staining was shown only in case of the number of REMS episodes. Discussion The activation of MCHergic hypothalamic neurons seems to be in a strong connection with the number of REMS, suggesting that REMS deficiency may be compensated via the enhancement of the number during the rebound rather than the average duration of REMS items. This work was supported by TAMOP‐2.2.1. B‐09/1/KMR‐2010‐0001