The GABA_A receptor (GABA_AR) is an ionotropic receptor and ligand-gated ion channel. Its endogenous ligand is γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system. Upon activation, the GABA_A receptor selectively conducts Cl⁻ through its pore, resulting in hyperpolarization of the neuron. This causes an inhibitory effect on neurotransmission by diminishing the chance of a successful action potential occurring. The reversal potential of the GABA_A-mediated IPSP in normal solution is −70 mV, contrasting the GABA_B IPSP.