Receivers GABAA

The receiving ionotropes GABA of the type has (GABA_A) have a great importance in term of human Physiologie. The Acide gamma-aminobutyrique (GABA) is the main thing inhibiting Neurotransmetteur in the Cerveau. Let us note here that the glycine plays this part on the level of the Spinal-cord, by activating channels GABA of the type C (GABA_C). These channels share important structural properties with the receivers with the Acétylcholine ionotropes and the receivers with the Sérotonine 5HT-3 ionotropes.

The GABA_A channels are the target of several pharmacological molecules of first importance in term of human health:

the Benzodiazepine S, like the Diazépam.
the Barbiturique S
the alcohol S, which explains their anesthetic effects
the Anesthésiques volatile generals

(gas), like the Halothane or the Chloroforme
intravenous, known as Hypnotique S, like the convulsant Propofol

, like the Picrotoxine
the gamma-hydroxybutyrate, sadly celebrates Drogue of rape

Channel chloride

The receiver is composed of five sub-units which organize in a pseudo-symmetrical way around a pore of conduction of the ions Chlorure S (and Bicarbonate S). Each sub-unit comprises a extra-membrane field containing the sites of fixing of the GABA and other effector, and a membrane hydrophobic field which defines the pore.

After co-operative fixing of two molecules of GABA, a change of conformation of the receiver makes it permeable in the passing ions chlorides. Those are engulfed then in the cell and hyperpolarisent it. This hyperpolarisation returns the passage of a wave of more difficult potential of action, because the threshold of activation of the sodic channels depending on the voltage becomes more distant. For this reason the GABA is a neuro-transmitter says inhibiting.

Family of the receivers " cys-loop"

The GABA_A channels belong to the family of the channels with five sub-units containing a bridge characteristic disulfide in the extracellular part (" cys-loop"). The other channels of this family are the receivers with the Acetylcholine muscular and neuronal, the receivers with the serotonin (5-HT3), the receivers with the Glycine of the spinal-cord, the receivers with the Glutamate (at the Insecte S).

references and notes

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