Gamma-aminobutyric acid receptor type B (GABA-B receptor)

The GABA-B receptor is a metabotropic, G protein-coupled receptor (GPCR) for gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter in the central nervous system (CNS). Unlike the ionotropic GABA-A receptors, which mediate fast synaptic inhibition, GABA-B receptors are responsible for slow and prolonged inhibitory effects. The functional GABA-B receptor is an obligate heterodimer composed of two subunits: GABA-B1 and GABA-B2. Activation leads to opening of potassium channels, inhibition of calcium channels, and inhibition of adenylyl cyclase, decreasing neuronal excitability and synaptic transmission. It is widely expressed throughout the CNS, regulating neuronal excitability and modulating neurotransmitter release. Clinical implications include roles in epilepsy, spasticity disorders, addiction biology, pain management, anxiety disorders, depression research.

Activation of Gi/o proteins leading to: - Opening of inwardly rectifying potassium channels (GIRKs), causing neuronal hyperpolarization. - Inhibition of voltage-gated calcium channels, reducing neurotransmitter release. - Inhibition of adenylyl cyclase activity, decreasing cAMP levels.