Stimulation of a ligand-gated receptor enables a channel in the receptor to open and permits the influx of chloride and potassium ions into the cell. The positive or negative charges that enter the cell either excite or inhibit the neuron. Ligands for these receptors include excitatory neurotransmitters, such as glutamate and, to a lesser extent, aspartate. Binding of these ligands to the receptor produces an excitatory postsynaptic potential (EPSP).