Profile of phosphatidylinositol metabolism stimulated by carbachol and glutamate in primary cultures of rat cerebellar neurons.

The formation of inositol phosphates, after stimulation of primary cultures of cerebellar neurons of the neonatal rat, in the presence of lithium chloride, by glutamate, carbachol, norepinephrine, histamine and Mg2+-free conditions, was measured by anion exchange high-pressure liquid chromatography (HPLC) with on-line radioactivity detection. All of the above agents caused a persistent, dose-dependent and calcium-sensitive preferential accumulation of inositol-4-phosphate, while the levels of inositol-1-phosphate were virtually unaffected. Agonist stimulation produced also a transient increase of a second peak which co-eluted with the standard for inositol 1,4-bisphosphate. However, no significant accumulation of inositol-1,4,5-trisphosphate and inositol-1,3,4,5-tetrakisphosphate was detected, possibly due to the fast kinetics of the metabolism of inositol phosphate. The results indicate that receptor-stimulated metabolism of inositol phosphate, in cultures of cerebellar granule cells, is due to a preferential hydrolysis of polyphosphoinositides and leads to the formation of inositol-4-phosphate through several calcium- and lithium-sensitive enzymatic steps.