The category of opioids includes both opiates, which are psychoactive drugs derived from opium, and a range of synthetic and non-synthetic drugs with pain-relieving effects. Many pharmaceutical opioids were developed as alternatives to morphine, a highly addictive pain medication with many potential adverse effects. Opioids including morphine are effective as painkillers because they can activate mu and delta opioid receptors, which when activated can block pain signals sent through the nervous system to the brain. Opioid receptors are abundant in areas of the brain where responses to psychoactive substances occur, including the dopamine reward pathway. Consequently, opioid use is both psychologically and biochemically addictive and can have a wide range of long-term effects on mental function, such changes to learning, reward, and stress responses.
[P1] Opioids work to block pain signals sent to the brain.