Depressant is a chemical agent that iminishes the function or activity of a specific part of the body (see also sedative). The term is used in particular with regard to the central nervous system (CNS). Alcohol is the most common example of a depressant. Many depressants acting on the CNS do so by increasing the activity of a particular neurotransmitter known as gamma-aminobutyric acid (GABA), although other targets such as the NMDA receptor, mu opioid receptor and CB1 cannabinoid receptor can also be important, depending on which drug is involved.