Structural determinants underlying high conductance GABA-A channels

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Large proteins called GABA-A receptors distributed widely throughout the brain are responsible for inhibition in most neurons. Many general anaesthetics, tranquillisers and anti-epileptic drugs act by modulating GABA-A receptors. Modern surgery would not be possible without rendering patients unconscious with general anaesthetics, but these valuable drugs still have unwanted side effects. For example, some of them affect cardiac and respiratory function. There is still a need for new, more effective general anaesthetics. One in every 200 people in Europe and North America suffers from epilepsy and 3% of the population suffers from anxiety. The leading general anaesthetics, anxiolytic and anti-epileptic drugs currently used, act on GABA-A receptors in the brain. The potential annual market for these drugs has been estimated to be US $2.7 billion. The world market for anaesthetics in 1999 was US $1.6 billion. All were discovered by serendipity. If the molecular site and mode of action of these drugs were understood, it is possible that new, more selective drugs could be discovered. The information gained in this project about GABA-A receptors is expected to be useful in understanding how these receptors work and in developing a new generation of drugs acting on GABA-A receptors. In this project we plan to examine what the functional consequences are and how GABA-A receptors colocalise in the membrane, akin to their physical state in the brain. We will examine the effects of drugs on receptors colocalised in the membrane. We have preliminary evidence suggesting that when GABA-A receptors are close to each other they open together so that their inhibitory response is maximised. Drugs are also able to make GABA-A receptors open in concert. The concept that receptors in the membrane talk to each other has been shown to occur for receptors from different classes but we now have evidence that the same type of receptors i.e. GABA-A receptors, are able to talk to each other.