However, several recent studies add to our understanding of such questions. Opioid peptide chemicals, like morphine, bind to opioid peptide receptor sites, and cause powerful analgesia. DNA transcripts RNA and RNA transcribes protein. It is the mu opiate receptor, or muOR, that we will review below. High levels of muOR are found in the periaqueductal gray of the midbrain and in the dorsal horn of the spinal cord.
Different individuals express the gene that transcripts the muOR protein differently.
In the summer of 1999, Uhl, Sora, and Wang10 published an article where they review recent work at their lab and the lab of others who are investigating the genetic basis for mouse and human differences in pain perception. Data from animal models provide powerful information for the understanding of genetic bases for individual differences in levels of human muOR gene expressions, and consequently in their perception of pain. If one has more muOR, then one perceives less pain. Studies on mice show that the lack of muOR results in increased perception of pain. This means that a lack of muOR renders one closer to threshold, making it easier to fire the nociceptor and to perceive pain.