Regional distribution of phosphoinositide-specific phospholipase C activity in rat brain

The phosphatidylinositol (PI) and phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolytic activities of phosphoinositide-specific phospholipase C (PLC) were measured in membrane and cytosol fractions from 7 discrete areas of the rat brain. Both the PI-PLC and PIP2-PLC specific activities were found to differ significantly among the 7 discrete brain areas. In the membrane fraction, the PIP2-PLC activity was higher than that of PI-PLC in each region, suggesting that the PLC in membranes prefers PIP2 to PI as substrate. The PIP2-PLC activities in the membrane were high in prefrontal cortex and cerebellum, but rather low in medulla oblongata and hypothalamus. The PI-PLC specific activity in the cytosol was significantly higher than that in the membrane of all brain areas examined. The PI-PLC specific activity in membranes is inversely proportional to its activity in the cytosol. In the cytosol fraction, the distribution pattern of PI-PLC specific activity resembled that of PIP2-PLC. These results indicate that PLCs are differently distributed in various regions of rat brain, and suggest the regional differences in neuronal transduction.