DIFFERENT CLASSES OF VOLUME TRANSMISSION SIGNALS EXIST IN THE CENTRAL-NERVOUS-SYSTEM AND ARE AFFECTED BY METABOLIC SIGNALS, TEMPERATURE-GRADIENTS AND PRESSURE WAVES

VOLUME transmission (VT) is the mode of intercellular communication in volving the diffusion of transmitters, via extracellular fluid (ECF) p athways, from nerve cells selectively capable of producing the signal (signal source) to nerve and glial cells selectively capable of recogn izing it (signal target). The proposal is now put forward that at leas t two classes of VT signals can be distinguished: (a) the private-code signals, exemplified by neurotransmitters, which are released by a li mited group of nerve cells and recognized, via high affinity G-protein coupled receptors or by cytosolic enzymes such as guanylate cyclase i n the case of nitric oxide, by a specific group of cells; and (b) the accessible-code signals, such as the electrical signals that are relea sed by all neuronal cells and decoded by almost every CNS cell. In the present paper, it will be underlined that carbon dioxide, hydrogen io ns, temperature gradients and pressure waves may be regulators of wiri ng transmission and VT.