| Obstructive sleep apnea (OSA) is a common sleep disorder, characterized by repeated episodes of airway obstruction during sleep resulting in intermittent hypoxemia. Previous studies proposed that reactive oxygen species (ROS) and apoptosis caused by intermittent hypoxia (IH) contributed to cognitive deficits. However, the exact mechanism is still poorly understood and not settled. Our recent studies, for the first time, showed that there is decreased expression of brain-derived neurotrophic factor (BDNF) in the hippocampus and impairment in long-term potentiation (LTP). Intra-brain injection of BDNF can effectively restore the magnitude of LTP. Thus, our study provides a novel mechanism and insight in the etiology of OSA-induced brain dysfunction in that lacking BDNF could be a critical factor.;In this study, ampakine application was used as "BDNF raiser" during 7-day IH and 14-day IH treatment by intraperitoneal (i.p.) injection. Four groups of adult male mice were used, two of them exposed to 7-day IH and two of them exposed to 14-day IH, each received either vehicle or ampakine i.p. injection. The paradigm of IH consisted of cycles of oxygen levels between 10% and 21% every 90s during the daytime for 8 hrs. Radial arm maze was used to investigate the performance of reference memory and working memory during the whole IH/ normoxia treatment from the first day. After that, expression of BDNF, ROS and molecular markers of apoptosis and morphology of hippocampal dendritic spines were examined, together with the investigation of both hippocamal synaptic plasticity, including early phase LTP (E-LTP) and late phase L-LTP (L-LTP).;Ampakine treatment restored the decreased level of hippocampal BDNF in the IH-treated group, as revealed by Western blot. Meanwhile, decreased ROS expression and alleviated cell death, including ER stress induced-apoptosis are all found in those ampakine injected groups. Golgi staining also showed that ampakine injection IH treatment rescued the decrease of mature dendritc spines, which is the structural basis of hippocampal synaptic plasticity, under 7-day IH treatment. Hippocampal long-term synaptic plasticity, which underlies the proposed mechanism of memory, was also found reversed in those ampakine injected groups, compared with groups under IH treatment.;Furthermore, results of radial arm maze showed that both the reference memory and working memory are impaired by 7-day IH treatment or 14-day IH treatment. However, the application of ampakine rescued IH-induced memory deficits.;Finally, by studying the effects of the ampakines on IH-induced neurocognitive dysfunction and LTP impairment, the role played by BDNF in OSA was further elucidated. These results were shed new lights on the exploration of novel pharmacological treatments in the OSA.;Alzheimer's disease is the most common cause of dementia among aged people. The causes of AD are not clear and onset of the disease is also not obvious. Iron is the most abundant trace metal in the brain and dysregulation of iron has been implicated in cell aging and a wide variety of neurodegenerative diseases including Alzheimer disease. However, up to now, very little is known about how iron accumulation is involved in Alzheimer disease.;To investigate whether high iron diet has any effects on normal or Alzheimer's disease, we introduced APPswe/ps1 transgenic mice, an Alzheimer's disease animal model, and used four groups in our study, namely wild type (wt) and APPswe/ps1 mice (tg), each with normal (ctrl) diets and high iron (HI) diet for at least 10 months.;Hippocampal LTP recording showed that wild type with high iron diet (wt-HI) decreased than that of wt-ctrl group. Tg-ctrl group also displayed decreased LTP level, including E-LTP and L-LTP, than that of wt-ctrl group. Strikingly, that of APPswe/ps1 under HI diets rescued the impaired hippocampal long-term synaptic plasticity than that of APPswe/ps1 mice under normal diets.;Results from radial arm maze also showed that both APPswe/ps1 with normal diet and wild type with HI diet had worse performance, either in reference memory or working memory, than those of wild type with normal diets. Again, it is surprised to find that performances of tg-HI group were much better than APPswe/ps1 mice under normal diet.;These results showed that the function of iron are very complicated, may have different effects on neural function of normal and AD objects. The detailed mechanisms needs to be further explored. |
