A sedative or tranquilliser[note 1] is a substance that induces sedation by reducing irritability[1] or excitement.[2] They are CNS depressants and interact with brain activity causing its deceleration. Various kinds of sedatives can be distinguished, but the majority of them affect the neurotransmitter gamma-aminobutyric acid (GABA). In spite of the fact that each sedative acts in its own way, most produce relaxing effects by increasing GABA activity.[3]