Calcium dynamics in the central nervous system.

Calcium ions are critically important in many functions of the nervous system from neurotransmitter release to intracellular signal transduction. The large difference between intracellular and extracellular calcium ion concentration ([Ca2+]) highlights the importance of the mechanisms controlling influx and efflux of this ion. Loss of the regulatory ability of these mechanisms and the subsequent increased intracellular calcium levels may be involved in pathological events of brain trauma, stroke, epilepsy and other diseases. Ca2+ dynamics in the CNS ranging from 'waves' to 'spirals' are being studied because of the availability of fluorescent indicators of Ca2+ combined with confocal microscopy. Cellular mechanisms of Ca2+ signal transduction have been extensively reviewed (Tsien and Tsein, 1990; Carafoli, 1992; Berridge, 1993; Berridge and Dupont, 1994; Pozzan et al., 1994; Clapham, 1995; Ghosh and Greenberg, 1995). The aim of this review is to present the types of Ca2+ dynamics observed in the CNS thus far, both in normal brain function as well as in response after injury.