GABA B receptor

GABA_B Receptor

The GABA_B receptor is a type of GABA receptor that is metabotropic, meaning it is a G-protein coupled receptor (GPCR). It is one of the two main types of receptors for gamma-aminobutyric acid (GABA), the primary inhibitory neurotransmitter in the central nervous system (CNS). Unlike the ionotropic [[GABA_A receptor]], which directly mediates fast synaptic inhibition, the GABA_B receptor mediates slower, prolonged inhibitory signals.

Structure

The GABA_B receptor is a heterodimer composed of two subunits: GABA_B1 and GABA_B2. These subunits are necessary for the receptor's function and are linked together to form a functional receptor complex. The GABA_B1 subunit is responsible for binding GABA, while the GABA_B2 subunit is essential for G-protein coupling and signal transduction.

Mechanism of Action

Upon binding of GABA to the GABA_B receptor, a conformational change occurs, activating the associated G-proteins. This activation leads to the inhibition of adenylate cyclase, a decrease in cyclic AMP (cAMP) levels, and the opening of potassium channels while closing calcium channels. The result is hyperpolarization of the neuron, making it less likely to fire an action potential, thus exerting an inhibitory effect.

Physiological Role

GABA_B receptors are widely distributed in the brain and spinal cord. They play a crucial role in modulating synaptic transmission, neuronal excitability, and synaptic plasticity. These receptors are involved in various physiological processes, including:

• Regulation of neurotransmitter release
• Modulation of pain perception
• Control of muscle tone
• Influence on cognitive function and memory

Clinical Significance

GABA_B receptors are implicated in several neurological and psychiatric disorders. Dysregulation of GABA_B receptor function has been associated with conditions such as:

• Epilepsy
• Anxiety disorders
• Depression
• Schizophrenia

Pharmacology

Agonists and antagonists of the GABA_B receptor are of significant interest in pharmacology. Baclofen, a GABA_B receptor agonist, is used clinically as a muscle relaxant and in the treatment of spasticity. Research is ongoing to develop more selective drugs targeting these receptors for therapeutic purposes.

See Also

• [[GABA_A receptor]]
• Neurotransmitter
• Central nervous system

References

• Bowery, N. G., & Enna, S. J. (2000). "Gamma-aminobutyric acid_B receptors: first of the functional metabotropic heterodimers." *Journal of Pharmacology and Experimental Therapeutics*, 292(1), 2-7.
• Bettler, B., Kaupmann, K., Mosbacher, J., & Gassmann, M. (2004). "Molecular structure and physiological functions of GABA_B receptors." *Physiological Reviews*, 84(3), 835-867.