DIFFERENCES BETWEEN MUSCARINIC-RECEPTOR-INDUCED AND CA-2+-INDUCED INOSITOL POLYPHOSPHATE ISOMER ACCUMULATION IN RAT CEREBRAL-CORTEX SLICES

Muscarinic-receptor stimulation or depolarization by elevated K+ leads to increased accumulation of [3H]Ins(1,4,5)P3, [3H]Ins(1,3,4,5)P4 and several degradation products of these polyphosphates separated by h.p.l.c. On the other hand, agents such as ionomycin and maitotoxin, which increase intracellular Ca2+ directly, produce a small accumulation of [3H]Ins(1,4,5)P3 and markedly increase [3H]Ins(1,4)P2, but [3H]Ins(1,3,4,5)P3, [3H]Ins(1,3,4)P3 and [3H]Ins(1,3)P2 are virtually unaffected. Ca2+-dependent [3H]inositol polyphosphate metabolism may involve different pools of lipids and/or phosphoinositidases.