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GABA receptors in the brain

What are GABA receptors?

The gamma-aminobutyric acid receptors (γ-aminobutyrate, GABA) are the most abundant brain receptors. GABA receptors are divided into ionotropic GABA A receptors (chloride channels) and metabotropic GABA B receptors.

GABA receptors are inhibitory and may require alcohol or sleeping pills. Indeed, gamma-aminobutyric acid (GABA) itself is sometimes sold as a nutritional supplement to facilitate sleep. However, such an effect has never been demonstrated in the oral administration of this neurotransmitter. The brain cells take care of the optimal supply of GABA for signaling purposes. We must not be tempted to consider GABA as an endogenous hypnotic that can be given orally.

Most brain neurons function to exhibit spontaneous activity that is continuously suppressed by gamma-aminobutyric acid through GABA receptors. Greater inhibition of some neurons may lead to activation of other neurons.

Alcohol and GABA receptors

Neuroscience for a long time of the last century was not sure how drunk alcohol actually causes drunkenness. Even at elementary school, a biology teacher told us that ethanol works by dissolving the fat of the lipid membrane of the cells and changing its permeability. Since then, however, it has come to light that a small molecule of ethanol affects a considerable number of specific nerve receptors and that the most important of these is the binding of ethanol to GABA A receptors.

Effect of ginseng on GABA receptors

GABA receptors are the most abundant receptors in the brain. Strong agonists or antagonists of these receptors are not found among adaptogens, but modulation effects are frequent.

Mechanism of action

Ginseng modelogene extract retards the uptake of GABA into synapses ( Tsang1985gsi ), which would theoretically increase the effect of GABA. However, a similar effect of ginseng was found in other neurotransmitters: glutamate, dopamine , noradrenaline and serotonin , so that the overall effect of ginseng on the CNS is not easily deductible and is not based on a single receptor.

Panaxosides related to GABA receptors

Ginsenosides Rb1, Rb2 , Rc , Re , Rf and Rg1 have been shown to have their reversible binding to GABA A and GABA B receptors ( Kimura1994igw ). The total saponin fraction as well as pure ginsenosides Re and Rf enhance the binding of flunitrazepam (Rohypnol) to GABA receptors ( Kimura1994igw ).

Total GABAergic effect of ginseng

The Panax quinquefolius extract at a dose of 3μg dry matter per milliliter dampened the activity of neurons in the brain stem (specifically nucleus tractus solitaria , rat) and counteracting 27% of the vagus irritation, twice less than the reference GABA agonist muscimol at the end. 30 μM. However, ginseng is not an agonist but a stabilizer: Ginseng extract protects neurons from higher doses of muscimol and this effect of ginseng is not a reversible GABA A bikunculin antagonist ( Yuan1998mag ). This would most likely indicate a neurosteroidal stabilizing effect. Also in panaxoside- majonoside-R 2 , its anti-stress action is shown to be at least partly due to the effect on GABA A receptors ( Huong1998aem ).

GABAergic effects in the realm of adaptogenes

(Of course, the list of GABAergic adaptogens is not exhausted.)

| 16.12.2009