Glossary · Mechanisms

GABA-A receptor

Also called: GABA-A, γ-aminobutyric acid receptor.

Definition: The GABA-A receptor is a ligand-gated chloride channel that mediates the brain's primary inhibitory neurotransmission. It is the target of benzodiazepines, alcohol, barbiturates, and the progesterone metabolite allopregnanolone — which is why bedtime oral micronized progesterone produces a calming, sleep-promoting effect.

Detailed definition

GABA-A receptors are pentameric ligand-gated ion channels that, when activated by gamma-aminobutyric acid (GABA), open a chloride channel and hyperpolarize the neuron, producing inhibition. They are the primary mediator of fast inhibitory neurotransmission in the brain. GABA-A receptors are heteromeric assemblies of various subunits (α, β, γ, δ, others), and the subunit composition determines pharmacology. Benzodiazepines (diazepam, lorazepam) bind a specific site on certain α-containing subunits and enhance GABA action. Alcohol, barbiturates, and general anesthetics also enhance GABA-A function. Neurosteroids — including allopregnanolone, the progesterone metabolite — bind a separate allosteric site and produce similar enhancement. This is the mechanism by which bedtime oral micronized progesterone produces calming and sleep-promoting effects.

Why it matters in menopause

Knowing the GABA-A receptor mechanism explains why bedtime oral progesterone often produces noticeable improvement in sleep within days, well before the slower effects of estradiol on hot flashes take hold. It also explains why morning progesterone can cause daytime sedation.

Sources

External references: Wikipedia.

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