The GABA receptor is a type of protein found in the brain that plays a crucial role in regulating neuronal activity. It responds to the neurotransmitter gamma-aminobutyric acid (GABA), which is the primary inhibitory neurotransmitter in the central nervous system. When GABA binds to its receptor, it typically causes the opening of ion channels, allowing negatively charged ions to enter the neuron, leading to a decrease in neuronal excitability. There are several subtypes of GABA receptors, primarily classified into GABA-A and GABA-B receptors. GABA-A receptors are ionotropic, meaning they directly control ion flow, while GABA-B receptors are metabotropic and work through secondary messenger systems. These receptors are essential for maintaining the balance between excitation and inhibition in the brain, influencing various functions such as mood, anxiety, and sleep.