ABSTRACT
In recent years, an effort has been made to understand the role of altered calcium homeostasis in different neurodegenerative conditions such as noise-induced hearing loss, ototoxicity, and aging. Calcium plays a crucially important role as an intracellular mediator in activating and regulating various physiological processes in neurons, including fast axonal transport, membrane excitability, cell motility, differentiation, synthesis and release of neurotransmitters, long-term potentiation, secretion, apoptosis, and synaptic plasticity (Ghosh and Greenberg, 1995). All of these processes must be tightly controlled, because neuronal activity can lead to marked increases in the concentration of cytosolic calcium. With concentrations of below 10
M
, intracellular calcium levels are kept at a level that is about four orders of magnitude below the extracellular calcium concentration of 2 to 5 m
M
.
