Local inflammatory response to dopaminergic neuronal death. (a) In normal SNpc tissue, microglia screen the brain parenchyma for changes. (b) In Parkinsonism, when dopaminergic neurons start dying, a number of signals, such as ATP or Ca2+, are released into the parenchyma. (c) These signals induce the inflammation, characterized by the enrolment of neighbor microglial cells and the recruitment of blood cells, such as T-cell lymphocytes or monocytes. (d) Microglial cells approach and contact damaged neurons. (d) Active microglial cells establish engulfing gliapses with degenerating neurons. (e) Microglial cells engulf and phagocytose degenerating neurons to resolve the local inflammation. The inflammatory response starts 24 h after the dopaminergic insult and is maintained during days until it is resolved. In mice, it could be resolved within 72 h, while in primates it could continue for years.
