Table 2.

Classification of the tunnelling-nanotube (TNT)- and extracellular-vesicle (EV)-mediated intercellular communication in the central nervous system into wiring transmission and volume transmission, respectively. See Schneider and Simons [24] and van der Pol et al. [25] for further information on extracellular-vesicle-mediated intercellular communication.

intercellular communication mode	channel	cargo transfer	mechanism of transport	origin
TNT type of WT (cultures of neuronal and glial cells)	TNT (15–60 µm long; 50–200 nm diameter) transient, membrane continuity between cells	organelles (especially vesicles), but also mtDNA, proteins, inside or along the TNT plasma membrane surface	actin-driven	no in vivo data in the CNS
EV type of VT (CNS: neurons, glial cells, brain endothelial cells)	extracellular space and CSF	exosomes (40–100 nm) containing proteins, lipids, mRNA, miRNA, mtDNA	diffusion and flow along energy gradients in the extracellular space	most cell types: plasma membrane; endosomes
		shedding vesicles: microvesicles (100–1000 nm) insufficiently known composition		most cell types: plasma membrane
		apoptotic bodies (1–4 µm) histones, DNA		all cell types: plasma membrane