Microglia
Research has discovered dystrophic (defective development) human microglia. "These cells are characterized by abnormalities in their cytoplasmic structure, such as deramified, atrophic, fragmented or unusually tortuous processes, frequently bearing spheroidal or bulbous swellings." The incidence of dystrophic microglia increases with aging. Microglial degeneration and death have been reported in research on Prion disease, Schizophrenia and Alzheimer's disease, indicating that microglial deterioration might be involved in neurodegenerative diseases. A complication of this theory is the fact that it is difficult to distinguish between "activated" and "dystrophic" microglia in the human brain.
Gliotransmitter
Gliotransmission can also occur between two types of glial cells: astrocytes and microglia. Calcium waves within the intracellular matrix of the astrocyte can cause a response in microglia with the presence of ATP in the extracellular matrix. One study demonstrated that a mechanical stimulation caused astrocytes to release ATP, which in turn caused a delayed calcium response in microglia, suggesting that astrocyte-to-microglia communication could be mediated by ATP.