GABA Receptor

Definition:

The GABA receptor, short for gamma-aminobutyric acid receptor, is a type of ionotropic receptor protein found in the central nervous system (CNS) of mammals, including humans. It is primarily responsible for mediating inhibitory synaptic transmission in the brain by binding to the neurotransmitter gamma-aminobutyric acid (GABA). GABA receptors are classified into two major types, known as GABA_A and GABA_B receptors, which differ in their structure, function, and pharmacology. These receptors play a crucial role in regulating the excitability of neurons and are the molecular targets of several drugs used to treat anxiety, epilepsy, insomnia, and other neurological disorders.

GABA_A Receptor

Structure:

GABA_A receptors are ligand-gated ion channels consisting of a pentameric assembly of different subunits. These subunits include two α (alpha), two β (beta), and one γ (gamma) subunit, although there are multiple subtypes of each subunit. The combination of different subunit compositions gives rise to functional diversity and pharmacological properties of GABA_A receptors. The binding sites for GABA and other drugs that modulate its function are located on the interface between α and β subunits.

Function:

Activation of GABA_A receptors by GABA leads to the opening of an ion channel, allowing chloride ions (Cl-) to enter the neuron. This influx of negative charges results in hyperpolarization of the neuronal membrane, making it less likely to generate an action potential. Consequently, GABA_A receptors play a crucial role in inhibiting neuronal excitability and maintaining the balance between neuronal inhibition and excitation. These receptors are widely distributed throughout the brain and are involved in various physiological processes such as motor control, cognition, memory, and anxiety regulation.

GABA_B Receptor

Structure:

GABA_B receptors are G-protein coupled receptors (GPCRs) composed of two subunits, GABA_B1 and GABA_B2. Upon activation, these receptors modulate the activity of ion channels through intracellular signaling mechanisms and various effector systems. They are primarily located on presynaptic terminals, where they regulate the release of neurotransmitters, including GABA itself, as well as other inhibitory and excitatory neurotransmitters.

Function:

GABA_B receptors are involved in long-term modulation of synaptic transmission. They exert inhibitory effects on neurotransmitter release through a mechanism known as presynaptic inhibition. By reducing neurotransmitter release, GABA_B receptors help regulate synaptic plasticity, neuronal excitability, and the overall balance of excitation and inhibition in the CNS. They have been implicated in several neurological conditions, such as epilepsy, pain perception, addiction, and psychiatric disorders.