Intracellular Calcium Homeostasis in a Human Neuroblastoma Cell Line: Modulation by Depolarization, Cholinergic Receptors, and α-Latrotoxin

Intracellular calcium homeostasis and its modulation by different agents was studied in control and differentiated IMR32 human neuroblastoma cells by using the Ca2+-sensitive fluorescent dye quin2. The results obtained demonstrate the existence in IMR32 cells of (a) voltage-dependent, verapamil sensitive, Ca2+ channels, which are expressed before differentiation; (b) muscarinic receptors whose activation triggers both Ca2+ influx and Ca2+ redistribution from intracellular stores, whereas nicotinic receptors and alpha-bungarotoxin binding sites do not; and (c) receptors for alpha-latrotoxin (the major toxin of the black widow spider venom), which are well-known markers of the neuronal presynaptic membrane. Up to now, no cell lines of human origin sensitive to this toxin have been identified. These results confirm that IMR32 cells are very convenient model cells for studying specific aspects of the neurochemistry and neurobiology of the human neuron at the molecular and cellular levels.