Opiates

How Nerve Cells Respond to Opiate

Within the limbic system, brainstem and spinal cord, there are places on certain nerve cells that recognize opiates. When stimulated by opiates, these sites -- called opiate receptors -- trigger responses in the brain and body.

Scientists have identified three types of opiate receptors: delta, mu and kappa (named after letters in the Greek alphabet). Each of these receptors is involved in different brain functions. For example, mu is responsible for the pain-relieving effects of the drug morphine.