INTRACELLULAR STORES AND CALCIUM SIGNALING IN MAMMALIAN SENSORY NEURONS

The injection of Ca ions into the cytoplasm through coordinated activi ty of calcium-permeable channels in the surface membrane and the membr anes of intracellular organelles is the main source of temporary eleva tion of the cytoplasmic free Ca2+ level ('the calcium signal') which t riggers cellular responses to various stimuli. In our experiments the contribution of intracellular Ca2+ stores to calcium signal generation was studied in two subpopulations of dorsal root ganglion (DRG) neuro nes using a combination of patch-clamp technique for measuring transme mbrane currents and fluorescent indicator indo-1 for estimating the ch anges in the cytoplasmic free Ca2+ level. Ca-induced Ca2+ release (CIC R) and inositol(1,4,5)-triphosphate (IP3)-induced Ca2+ release (IICR) were found to be functional only in certain types of sensory neuronal cell, presumably in neurones transmitting tactile and proprioceptive i nformation. Mitochondrial Ca2+ accumulation and release was found to p articipate in the shaping of calcium signals in both subpopulations of DRG neurones. (C) 1997 Elsevier Science S.A.