The pain relief effect of opioids is induced by the synergy of two events, namely reduction of pain threshold and emotional detachment from pain.
Opioids alleviate pain at the spinal level by raising the threshold of pain. If a person is treated with opioids, he will experience less pain in the presence of a painful stimulus. However the main painkiller effect of opiates is not only an increase in the pain threshold, but also an attenuation of the individual’s subjective evaluation of pain, i.e. they have a conscious response to pain, that is modified by opioids. The impressive abundance of opiate receptors in the limbic system suggests an explanation for the emotional changes caused by opioid use. The limbic system, a set of structures located immediately below the cerebral cortex, contains the highest amount of opioid receptors as compared to other parts of the brain.
