In the absence of GABA, benzodiazepines have no effects on GABA-A receptor function. It is important to recognize that benzodiazepines increase the frequency of opening of the GABA-A receptor Cl– channel in the presence of GABA. The influx of the chloride anion results in hyperpolarization of the neuron resulting in CNS depression. Activation of the BZ-R causes a conformational change to a central pore, which allows the entrance of chloride ions into the neuron. The extracellular portions of the alpha and gamma subunit proteins form a binding site for benzodiazepines. The extracellular portions of the alpha and beta subunit proteins form a receptor site for gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter. The five subunits comprise of two alpha subunits, two beta subunits, and one gamma subunit. The receptor is a protein comprised of five transmembrane subunits that form a chloride channel in the center, i.e., the GABA-A receptor. Benzodiazepines are a class of drugs that act upon benzodiazepine receptors (BZ-R) in the central nervous system (CNS).
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