Inositol phospholipid hydrolysis as a primary response to receptors not linked to adenylate cyclase.

Activation of several receptors by neurotransmitters, hormones and local mediators stimulate inositol phospholipid breakdown by phospholipase C in a variety of tissues. Inositol trisphosphate and diacylglycerol are probable second messengers for these receptors with the former mobilizing intracellularly bound calcium and the latter stimulating a cyclic nucleotide independent protein kinase C. Activation of these receptors also often leads to a stimulation of arachidonic acid metabolism generating prostaglandins, leukotrienes etc. In the brain, several neurotransmitters including neuropeptides stimulate inositol phospholipid breakdown by interacting with receptors closely coupled to phospholipase C. Furthermore, depolarization of cerebral cortical slices also stimulates inositol phospholipid breakdown by opening voltage- and dihydropyridine-sensitive calcium channels.