The Mitoflash In Primary Hippocampal Neuron

Mitoflash,a widely preserved subcellular phenomenon from bacteria to mammals,was found to be a complex event,including alkalization of mitochondrial matrix,burst generation of superoxide and depolarization of mitochondrial membrane potential(??)etc.Previous studies have implied that mitoflashes could be involved in a variety of physiological and pathological processes.In this study,for the first time,we characterized dynamics and chemical properties of mitoflash in primary hippocampal neuron,established a powerful method to trigger mitoflash at single-mitochondrial level and further explored the relationship between dendritic mitoflash and synaptic plasticity.We found that neuronal mitoflash have preserved most of the chemical properties exhibited in other systems,like alkalization of mitochondria matrix,burst generation of reactive oxygen species and depolarization of ??,with a small amount of differences.In addition to single-mitochondrion level mitoflash as reported in other systems,we observed a burst generation of whole-cell wide synchronized mitoflashes in bicuculline-treated neurons,which may fire epileptic activity.Further experiments implied there was a correlation between intracellular calcium oscillation and the mitoflash occurrence.Furthermore,by applying two-photon laser pulse at a single spot of a mitochondrion,we were able to induce a typical mitoflash within 1ms in the target mitochondrion.Next,we found a positive correlation between long-term spine enlargement and mitoflash events.A classical protocol was employed to induce non-specific synaptic long-term potentiation in neurons,10min after induction,dendritic mitoflash events started to increase,the frequency had increased about 7 times at peak,and then gradually decreased to baseline about 40min after the stimuli.This mitoflash frequency phasic increase was NMDA receptor-dependent and required the activation of CaMKII.In addition,we found that those mitochondria had increased mitoflash activity was in adjacent to at least one enlarged dendritic spine,however,mitochondria adjacent to stable spines showed no significant structural change.Moreover,there was at least one mitoflash in the dendritic base of the enlarged spines rather than stable spines after LTP induction.These result indicates local mitoflash is intimately related to spines underwent structural long-term potentiation.A step further,by inducing 1-2 laser-activated mitoflashes in the adjacent mitochondrion in the time window of 20min-30min after short-term potentiation induction,spines underwent short-term enlargement could be converted into long-term enlargement(data not shown).These results pointed out the significant role of mitoflash in long-term potentiation.