Receptor-stimulated inositol phospholipid hydrolysis and neural function.

Many transmitters in the brain act by stimulating the hydrolysis of an inositol lipid (phosphatidylinositol 4,5-bisphosphate) to give diacylglycerol (DG) and inositol 1,4,5-trisphosphate (Ins1,4,5P3). These two second messengers mark the beginning of a highly versatile signalling system which may have a unique role in modulating neural activity. By mobilizing calcium from intracellular stores, Ins 1,4,5P3 may regulate the calcium set-point thereby effecting both excitability and facilitation. The DG/C-kinase pathway, through its ability to modulate a variety of physiological processes, may regulate both transmitter release and excitability. Some of the changes in excitability seem to depend upon changes in potassium permeability. Receptor-stimulated inositol lipid hydrolysis may thus play a central role in neural function by modulating transmitter release through subtle alterations in excitability.