Glutamate (neurotransmitter)
In neuroscience, glutamate refers to the anion of glutamic acid in its role as a neurotransmitter: a chemical that nerve cells use to send signals to other cells. It is by a wide margin the most abundant excitatory neurotransmitter in the vertebrate nervous system. It is used by every major excitatory function in the vertebrate brain, accounting in total for well over 90% of the synaptic connections in the human brain. It also serves as the primary neurotransmitter for some localized brain regions, such as cerebellum granule cells.
Neurotoxin
Though nitric oxide (NO) is commonly used by the nervous system in inter-neuron communication and signaling, it can be active in mechanisms leading to ischemia in the cerebrum (Iadecola 1998). The neurotoxicity of NO is based on its importance in glutamate excitotoxicity, as NO is generated in a calcium-dependent manner in response to glutamate mediated NMDA activation, which occurs at an elevated rate in glutamate excitotoxicity. Though NO facilitates increased blood flow to potentially ischemic regions of the brain, it is also capable of increasing oxidative stress, inducing DNA damage and apoptosis. Thus an increased presence of NO in an ischemic area of the CNS can produce significantly toxic effects.