Figure 1.

Schematic of wiring transmission and volume transmission in neural networks. Wiring transmission is illustrated by means of a synaptic contact. Volume transmission is the diffusion and flow of signals in the extracellular space (ECS) of the brain and in the cerebrospinal fluid (CSF) along the energy gradients. Thus, VT is illustrated as: the local extrasynaptic diffusion of neurotransmitters in the ECS; the long-distance diffusion and flow of some classical neurotransmitters and neuropeptides in the ECS; the flow of VT chemical signals via the CSF. Finally, the effects of the pressure waves in cerebral arteries on the diffusion and flow of the VT signals in the ECS and CSF are indicated (see [6,7,12,13]).