GABA receptor protein

Animal studies have suggested a possible mechanism for tolerance, in that chronic treatment of rats with triazolam reduced the mRNA coding for certain GABA receptor proteins (111). 

All cell membranes contain transmembrane proteins that form ion channels. These ion channels are usually selectively permeable to particular ions. Some channels, such as GABA-gated ion channels, are permeable to Cl ions and are inhibitory in nature because they make the inside of the nerve or muscle cells more negative as the Cl ions enter. Some ion channels are permeable to the cations Na and K, and an example of this type is the nicotinic acetylcholine-gated channel. Nicotinic channels have an excitatory effect when they open because Na ions enter and K ions leave through these channels. The cell becomes more positive inside and depolarizes. If the cell is a muscle cell, calcium accumulates in the cytoplasm and it contracts. We have found that all over the surface of Ascaris muscle there are GABA receptors (Martin, 1980) as well as nicotinic acetylcholine channels (Martin, 1982 Robertson and Martin, 1993). 

Molecular Neuropharmacology Strategies and Methods is intended to bridge the gap between molecular biology and advanced chemistry. In addition, it attempts to include information about x-ray crystallographic analyses whenever available. This book discusses interdisciplinary interactions for monoamine transporters, amino acid transporters, ionotropic receptors, metabotropic glutamate receptors, GABA receptors, and other G protein-coupled receptors. 

Ga-GDP has no affinity for the effector protein and reassociates with the p and Y subunits (A). G-proteins can undergo lateral diffusion in the membrane they are not assigned to individual receptor proteins. However, a relation exists between receptor types and G-protein types (B). Furthermore, the a-subunits of individual G-proteins are distinct in terms of their affinity for different effector proteins, as well as the kind of influence exerted on the effector protein. G -GTP of the Gs-protein stimulates adenylate cyclase, whereas G -GTP of the Gr protein is inhibitory. The G-protein-coupled receptor family includes muscarinic cholinoceptors, adrenoceptors for norepinephrine and epinephrine, receptors for dopamine, histamine, serotonin, glutamate, GABA, morphine, prostaglandins, leukotrienes, and many other mediators and hormones. 

No difference has been observed in the interactions of the two enantiomers of isoflurane with hpid bilayers. But the (5)-enantiomer of isoflurane is two times more active than the (7 )-enantiomer toward a calcium channel receptor, that is sensitive to volatile anesthetic agents, while nodifference in activity has been observed toward an anesthetic nonsensitive receptor. The (5)-enantiomer of isoflurane is also more active than the (R)-enantiomer toward acetylcholine nicotinic receptor and GABA receptor. These data strongly suggest that fluoroethers interact not only with cerebral membranous lipids but also with receptor proteins. 

Benzodiazepines facilitate inhibition by y-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the brain. The benzodiazepine receptor is a subtype of the GABA receptor. Activation of the benzodiazepine receptor facilitates the action of endogenous GABA, which results in the opening of chloride ion channels and a decrease in neuronal excitability. Benzodiazepines act rapidly because ion channels can open and close relatively quickly, in contrast to the slower onset of action that occurs with G protein-linked receptors. 

Less is known about GABAg receptor structure. GABAg receptors are coupled indirectly to K+ channels. These receptors, which are always inhibitory, are coupled to G-proteins. When activated, GABAg receptors decrease Ca + conductance and inhibit cAMP production. The GABA, receptor is probably little more than a subtype of the GABA receptor. It contains the p subunit peptide and is located primarily, if not exclusively, in the retina. 

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