ROD-188 is a sedative

Sedative

A sedative or tranquilizer is a substance that induces sedation by reducing irritability or excitement....

 drug structurally derived from the GABA_A antagonist bicuculline

Bicuculline

Bicuculline is a light-sensitive competitive antagonist of GABAA receptors. It was originally identified in 1932 in plant alkaloid extracts and has been isolated from Dicentra cucullaria, Adlumia fungosa, Fumariaceae, and several Corydalis species. Since it blocks the inhibitory action of GABA...

. Unlike bicuculline, ROD-188 acts as an agonist

Agonist

An agonist is a chemical that binds to a receptor of a cell and triggers a response by that cell. Agonists often mimic the action of a naturally occurring substance...

 at GABA_A receptors, being a positive allosteric modulator acting at a novel binding site distinct from those of benzodiazepines, barbiturates or muscimol

Muscimol

Muscimol is the major psychoactive alkaloid present in many mushrooms of the Amanita genus. Unlike psilocin , which is a serotonergic psychedelic and agonist for the 5-HT2A receptor set, muscimol is a potent, selective agonist for the GABAA receptor set and is a deliriant as a opposed...

, with its strongest effect produced at the α6β2γ2 subtype of the GABA_A receptor. ROD-188 is one of a number of related compounds acting at this novel modulatory site, some of which also act at benzodiazepine receptors.