Depressant

A depressant drug, referred to in slang as a "downer", is a chemical agent that diminishes 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 NMDA receptor, mu-opioid receptor and CB1 cannabinoid receptor can also be important, depending on which drug is involved.