REM Sleep Deprivation Reverses Neurochemical and Other Depressive-Like Alterations Induced by Olfactory Bulbectomy

There is compelling evidencethatsleep deprivation (SD) is an effective strategy in promoting antidepressant ef- fects in humans, whereas few studies were performed in relevant animal models of depression. Acute administration of antidepressants in humans and rats generates a quite similar effect, i.e., suppression of rapid eye movement (REM) sleep. Then, we decided to investigate the neurochemical alterations generated by a protocol of rapid eye movement sleep depri- vation (REMSD) in the notably known animal model of depression induced by the bilateral olfactory bulbectomy (OBX). REMSD triggered antidepressant mechanisms such as the increment of brain-derived neurotrophic factor (BDNF) levels, within the substantia nigra pars compacta (SNpc), which were strongly correlated to the swimming time (r=0.83; P<0.0001) and hippocampal serotonin (5-HT) content (r=0.66; P=0.004). Moreover, there was a strong correlation between swimming time and hippocampal 5-HT levels (r=0.70;P=0.003), strengthen the notion of an antide- pressant effect associated to REMSD in the OBX rats. In addition, REMSD robustly attenuated the hippocampal 5-HT deficiency produced by the OBX procedure. Regarding the rebound (REB) period, we observed the occurrence of a sustained antidepressant effect, indicated mainly by the swim- ming and climbing times which could be explained by the maintenanceoftheincreasednigralBDNFexpression.Hence, hippocampal 5-HT levels remained enhanced in the OBX group after this period. We suggested that the neurochemical complexity inflicted by the OBX model, counteracted by REMSD, is directly correlated to the nigral BDNF expression and hippocampal 5-HT levels. The present findings provide new information regarding the antidepressant mechanisms triggered by REMSD.