title: Effects of hypoxic preconditioning on synaptic ultrastructure in mice.
abstract: Hypoxic preconditioning (HPC) elicits resistance to more drastic subsequent insults, which potentially provide neuroprotective therapeutic strategy, but the underlying mechanisms remain to be fully elucidated. Here, we examined the effects of HPC on synaptic ultrastructure in olfactory bulb of mice. Mice underwent up to five cycles of repeated HPC treatments, and hypoxic tolerance was assessed with a standard gasp reflex assay. As expected, HPC induced an increase in tolerance time. To assess synaptic responses, Western blots were used to quantify protein levels of representative markers for glia, neuron, and synapse, and transmission electron microscopy was used to examine synaptic ultrastructure and mitochondrial density. HPC did not significantly alter the protein levels of astroglial marker (GFAP), neuron-specific markers (GAP43, Tuj-1, and OMP), synaptic number markers (synaptophysin and SNAP25) or the percentage of excitatory synapses versus inhibitory synapses. However, HPC significantly affected synaptic curvature and the percentage of synapses with presynaptic mitochondria, which showed concomitant change pattern. These findings demonstrate that HPC is associated with changes in synaptic ultrastructure.
authors.affiliation: China-America Joint Institute of Neuroscience, CAJIN, Xuanwu Hospital, Capital Medical University, Beijing, China; Neuroprotection Research Laboratory, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts; Neuroprotection Research Laboratory, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.forename: Zhishan
authors.initials: Z
authors.lastname: Sun
authors.forename: Shufeng
authors.initials: S
authors.lastname: Sun
authors.forename: Yunxia
authors.initials: Y
authors.lastname: Duan
authors.forename: Jingfei
authors.initials: J
authors.lastname: Shi
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Qi
authors.forename: Ran
authors.initials: R
authors.lastname: Meng
authors.forename: Yongxin
authors.initials: Y
authors.lastname: Sun
authors.forename: Xianwei
authors.initials: X
authors.lastname: Zeng
authors.forename: Dehua
authors.initials: D
authors.lastname: Chui
authors.forename: Xunming
authors.initials: X
authors.lastname: Ji
mesh_terms: D000818:Animals; D015153:Blotting, Western; D000860:Hypoxia / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D008813:Mice, Inbred ICR; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000502:physiology / Q000648:ultrastructure; D009433:Neural Inhibition / Q000502:physiology; D009830:Olfactory Bulb / Q000503:physiopathology / Q000648:ultrastructure*; D011897:Random Allocation; D012018:Reflex / Q000502:physiology; D013569:Synapses / Q000502:physiology / Q000648:ultrastructure*
keywords: hypoxic preconditioning; presynaptic mitochondria; synaptic curvature