Figure 4.

Prolongation of contacts between microglia processes and presynaptic boutons in response to cerebral ischemia and sequential loss of presynaptic bouton. A, z-stacked images of microglial processes (yellow arrow) and presynaptic boutons (blue arrows). Continuous images were acquired from the ischemic penumbra ∼500 μm apart from the ischemic core and commenced ∼30 min after MCA occlusion. Note that the contact between the microglial processes and the boutons lasted for >60 min, whereas it is very constant in duration about 5 min in the control brain (see text). In addition, the bulbous nature of the tip of the microglial processes once in contact with the pre(post)synaptic structures in the control (Fig. 1 B) were not evident in the ischemic brains. Top left image shows a microglial process before contact, indicated as 0 min, and bottom right shows the same process just after retraction. Scale bars, 5 μm. B, The presynaptic bouton (indicated by the blue arrow) in the ischemic penumbra disappeared after the prolonged contact with a microglial process (yellow arrow). Note that the microglial process in this example crept forward and backward along the axon (top two panels) and gradually approached one of boutons (lower left bouton, blue arrow). Scale bars, 2 μm.