Rapid fragmentation of the endoplasmic reticulum in cortical neurons of the mouse brain in situ following cardiac arrest.

Neuronal endoplasmic reticulum (ER), continuous from soma to dendritic spines, undergoes rapid fragmentation in response to N-methyl-D-aspartate (NMDA) receptor stimulation in hippocampal slices and neuronal primary cultures. Here, we show that ER fragments in the mouse brain following cardiac arrest (CA) induced brain ischemia. The ER structure was assessed in vivo in cortical pyramidal neurons in transgenic mice expressing ER-targeted GFP using two-photon laser scanning microscopy with fluorescence recovery after photobleaching (FRAP). Endoplasmic reticulum fragmentation occurred 1 to 2 minutes after CA and once induced, fragmentation was rapid (<15 seconds). We propose that acute ER fragmentation may be a protective response against severe ischemic stress.