Alteration of [3H] Ins (1,4,5) P3 and [3H] PDBu Binding Sites in Brains of Patients with Parkinson’s Disease and Multiple System Atrophy

The roles of membrane inositol phospholipid turnover in intracellular signal transduction have been vigorously researched. Stimulation of several receptors by neurotransmitters, hormones, and growth factors leads to accelerated turnover of polyphosphoinositides. Hydrolysis of phosphatidylinositol 4,5-bisphosphate by activated phospholipase C generates inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) and 1,2-diacylglycerol, both of which act as second messengers. The former increases intracellular Ca2+ and the latter activates protein kinase C (PKC) (Nishizuka, 1986).