Cation-Chloride Cotransporters in Neuronal Communication.

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.