[Glutamate in brain: transmitter and poison].

Glutamate is a key excitatory neurotransmitter in the central nervous system (CNS). In addition, glutamate has a key role during the brain development, e.g., in synaptogenesis and in adult CNS, glutamate has an important role in learning and memory processes. Glutamate achieves its role through a variety of receptors, ionotropic (NMDA and AMPA) and metabotropic. Large number of glutaminergic synapses combined with wide distribution through the brain makes CNS particularly vulnerable towards uncontrolled release of glutamate such as observed during ischemia and postischemia. It is glutamate--its excitotoxic action--that is often considered as a key player in postichemic brain damage. However, despite the significant role of the neurotransmitter in pathogenesis of ischemic brain damage (in particular in focal brain ischemia), a complexity of metabolic events occuring during and after ischemia must be taken into account, glutamatenot being the solely culprit for the nerovus tissue damage.