The ionotropic GABA A receptor

K. Krnjevic and S. Schwartz observed in 1967 that γ-aminobutyric acid (GABA), applied by microiontophoresis on intracellularly recorded cortical neurons, evokes a hyperpolarization of the neuronal membrane which has properties similar to synaptically evoked hyperpolarization. This led to the hypothesis that GABA mediates inhibitory synaptic transmission in the adult vertebrate central nervous system. GABA released by presynaptic terminals activates two main types of receptors: (i) ionotropic receptors called GABA A and (ii) metabotropic receptors, i.e. receptors coupled to GTP-binding proteins called GABA B receptors. The aim of the present chapter is to study how a GABA A receptor converts the binding of two GABA molecules to a rapid and transient change of the membrane potential in the adult vertebrate central nervous system.