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 delivery of GABA for signaling purposes. We must not be tempted to consider GABA as an endogenous hypnotic that can be administered orally.
Most brain neurons function to exhibit spontaneous activity that is continuously suppressed by gamma-aminobutyric acid over 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 in the fat of the lipid membrane of 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 common.
Mechanism of action
The 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 with other neurotransmitters: glutamate, dopamine , noradrenaline and serotonin , so that the overall effect of ginseng on the CNS is not easily deductible and does not involve single receptor interactions.
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 of dry matter per milliliter, inhibited brain neuronal activity (specifically, the nucleus tractus solitaria , rat) and counteracting 27% vagal excitation, twice less than the reference GABA agonist muscimol at conc. 30 μM. Ginseng is not an agonist but a stabilizer: Ginseng extract protects neurons from higher doses of muscimol and this ginseng effect is not a reversible GABA A bikunculin antagonist ( Yuan1998mag ). This would most likely indicate a neurosteroidal stabilizing effect. Also in the panaxoside- majonoside-R 2 , its anti-stress action is shown to be at least partly due to the effect on GABA A receptors ( Huong1998aem ).
GABAergy effects in the realm of adaptogens
- The sedative effect of Bajkal canine can be blocked by the GABA antagonist bikuline ( Chang2011beb ).
(Of course, the list of GABAergic adaptogens is not exhausted.)