GABA and glutamate, amino acid transmitters
Gamma-amino butyric acid and glutamic acid are amino acid neurotransmitters or modulators which modify cellular polarization by activating receptors, particularly neuronal plasma membrane receptor-channels.
Extracellular and intracellular concentrations of Na+, K+, Ca2+ and Cl- ions are very different. The extracellular concentrations of Na+ and Cl- is approximately 10 times higher than their intracytoplasmic concentration, that of Ca2+ is approximately 10.000 times higher.
The opening of a channel in the plasma membrane of a cell, specific for an ion, induces the influx into the cell either of Na+ or Ca2+, inducing a depolarization, or of Cl-, inducing an hyperpolarisation.
Amino acid neurotransmitters: gamma-amino butyric acid or GABA, glycine, ß-alanine and taurine, which open chloride receptors-channels induce cellular hyperpolarisation by increasing intracellular concentration of chloride, are inhibitors.
The amino acid transmitter glutamate which opens receptors channels inducing an intracellular influx of Na+ and Ca2+ ions and a depolarization, is excitatory.
There are many other membrane structures involved in the regulation of influx and efflux of sodium, potassium, calcium and chloride ions.