Pain Killing Protein Is Eight Times More Powerful than Morphine

Pain researchers have identified a protein produced by neurons that when injected into the spinal columns of experimental mice suppressed pain eight times more effectively than morphine did.

The protein under investigation, prostatic acid phosphatase (PAP) was shown by investigators at the University of North Carolina (Chapel Hill, USA) to be the same as a well-known neuron biomarker, fluoride-resistant acid phosphatase (FRAP). This became apparent when mice genetically engineered to lack PAP activity were found to also lack FRAP.

The genetically engineered mice were more sensitive than normal mice to inflammatory pain and neuropathic pain, two common forms of chronic pain in humans. Furthermore, data published in the October 9, 2008, issue of the journal Neuron revealed that the increased pain sensitivities of the engineered mice diminished when they received injections of excess amounts of PAP into their spinal cords. The effectiveness of PAP injections was estimated to be about eight times that of morphine. Additionally, a single dose of PAP provided pain relief for up to three days, considerably longer than the five hours obtained from a dose of morphine.

"We were really blown away that a simple injection could have such a potent effect on pain,” said first author Dr. Mark J. Zylka, assistant professor of cell and molecular physiology at the University of North Carolina. "Not only that, but it appeared to work much better than the commonly used drug morphine. This protein has the potential to be a groundbreaking treatment for pain and has previously not been studied in pain-sensing neurons. It is entirely possible that PAP itself could be used as a treatment for pain, through an injection just like morphine, but we would like to modify it to be taken in pill form. By taking this field in a new direction, we are encouraged and hopeful that we will be able to devise new treatments for pain.”

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