Glutamate is a powerful excitatory neurotransmitter that is released by nerve cells in the brain. It is responsible for sending signals between nerve cells, and under normal conditions it plays an important role in learning and memory. There are two general ways, however, that glutamate can actually be damaging to nerve cells and the brain as a whole. First, there can be too much glutamate around; abnormally high concentrations of glutamate can lead to overexcitation of the receiving nerve cell. Second, the receptors for glutamate on the receiving nerve cell can be oversensitive, such that less glutamate molecules are necessary to excite that cell.
In both cases, cells activated by glutamate become overexcited. This overexcitation can lead to effects that can cause cell damage and/or death. For this reason, glutamate is referred to as an excitotoxin when it causes cellular damage. Scientists have found that certain glutamate receptors in the nerve cells of patients with HD tend to be oversensitive to glutamate. For some patients with HD, glutamate can act as an excitotoxin, even if its levels are not particularly high. Treatments that attempt to inhibit glutamate activity therefore may have some therapeutic potential.
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