Abstract
Two isoforms of the cation-Cl cotransporter family are expressed in neurons and modulate neurotransmission. NKCC1, a Na+-K+-2Cl cotransporter, by raising internal Cl, is responsible for excitatory GABAergic activity in immature brain and in adult sensory neurons. KCC2, a neuronal-specific isoform of the K+-Cl cotransporter, by lowering internal Cl, is critical for inhibitory GABA responses in mature central nervous system neurons.