the analgesic effect of opioids is due to their
Opioid Opioids are substances that act on opioid receptors to produce morphine-like effects.[2] Medically they are primarily used for pain relief, including anesthesia.[3] Other medical uses include suppression of diarrhea, treating opioid use disorder, reversing opioid overdose, suppressing cough, and suppressing opioid induced constipation.[3] Extremely potent opioids such as carfentanil are only approved for veterinary use.[4] Opioids are also frequently used non-medically for their euphoric effects or to prevent withdrawal.[5]
Dopamine receptor Dopamine is the primary neurotransmitter involved in the reward pathway in the brain. Thus, drugs that increase dopamine signaling may produce euphoric effects. Many recreational drugs, such as cocaine and substituted amphetamines, inhibit the dopamine transporter (DAT), the protein responsible for removing dopamine from the neural synapse. When DAT activity is blocked, the synapse floods with dopamine and increases dopaminergic signaling. When this occurs, particularly in the nucleus accumbens,[31] increased D1[28] and decreased D2[31] receptor signaling mediates the "rewarding" stimulus of drug intake.[31]