McGill findings offer new clue for pain hypersensitivity

A new study by McGill University researcher Remi Quirion, PhD, represents a possible breakthrough in better understanding and treating hyperalgesia, or extreme sensitivity to pain. The findings, published in the current (Oct. 24) issue of the Proceedings of the National Academy of Sciences, identify for the first time the powerful pain-inducing properties of the protein adrenomedullin (AM).

"Previous research characterized AM as protein with many biological functions, including cell proliferation and inflammation," said Dr. Quirion, principal investigator in the study, professor of psychiatry at McGill and Scientific Director of the Douglas Hospital Research Centre. "Our findings are the first to demonstrate its significant role in pain modulation, particularly in long-lasting heat hypersensitivity and hyperalgesia."Hyperalgesia is an extreme sensitivity to pain, sometimes caused by damage to nerve endings. It can be experienced in specific areas or in a more generalized form. The discovery of this new pain-related protein that causes hyperalgesia could help enormously in developing new antagonists, or analgesics, to block pain.Quirion and his colleagues used an animal model to characterize the pain-inducing role of AM. Using biochemical and microscopy techniques, they demonstrated for the first time that AM is present in the nerve endings of cells capable of perceiving pain. When they injected AM into rats, a gentle stimulus not normally considered painful elicited a pain response. Conversely, blocking or intercepting the AM signalling reversed this hyperalgesic effect."Our results clearly demonstrate this new pain-inducing role for AM," says Quirion. "This is groundbreaking and opens a new avenue for pain research and treatment."(Source: Proceedings of the National Academy of Sciences : McGill University : November 2006.)