**8. Glial cells**

There are greater number of glial cells than neurons (between five and ten times more) in CNS. Different types of cells comprise glia. For example, astrocytes, radial glia, and oligodendroglia are of neural origin, whereas microglia are differentiated blood monocytes during ontogeny, where neurons develop first, and glial cells develop later. Glial cells exert a profound effect on neuronal development by providing trophic support essential for neuronal survival and are involved in neuronal

#### **Figure 2.**

*Schematic diagram depicting the influence of ACh as well as the roles of mAChRs and nAChRs (primarily alpha7 subtype) in microglia and astroglia modulation of pre- and post-synaptic neurons. Note the production of ROS and NO by microglia as well as interaction of Aβ with both nicotinic and muscarinic receptors.*

migration, axon, and dendrite outgrowth, and in synaptogenesis (**Figure 2**) [36]. Below, the role of microglia and astrocytes in AD pathology and the influence of cholinergic system on them is discussed in more detail.
