When disturbed, an accumulation of glutamate occurs as a result of a mutation in the glutamate transporters, which act like pumps to drain glutamate from the brain. This causes glutamate concentration to be several times higher in the blood than in the brain; in turn, the body must act to maintain equilibrium between the two concentrations by pumping the glutamate out of the bloodstream and into the neurons of the brain. In the event of a mutation, the glutamate transporters are unable to pump the glutamate back into the cells; thus a higher concentration accumulates at the glutamate receptors.