Australian and American scientists have found a way to halt a reaction in the brain that causes the side effects of morphine, potentially laying the groundwork for more effective therapeutic drugs.
The team from the University of Adelaide and the University of Colorado has discovered how opioid drugs such as morphine produce an inflammatory response in the brain - by activating an immune receptor.
This can cause patients to develop tolerance to the drug, and increased sensitivity to pain.
But in an article published in the Proceedings of the National Academy of Sciences, the team has demonstrated how to block the receptor.
“For some time it’s been assumed that the inflammatory response from morphine was being caused via the classical opioid receptors,” said study co-author Mark Hutchinson, Research Fellow at the University of Adelaide’s School of Medical Sciences.
“However, we found instead that morphine binds to an immune receptor complex called toll-like receptor 4, and importantly this occurs in a very similar way to how this receptor detects bacteria.”
The team has been developing drugs to block the immune receptor in mice. Eventually, the research could allow doctors to administer less morphine to humans to provide greater pain relief, Dr Hutchinson said.
“Our experiments in mice have shown that if this relationship with the immune receptor is disrupted, it will prevent the inflammatory response. This is an exciting result because it opens up possibilities for future drugs that promote the beneficial actions of morphine while negating some of the harmful side effects.”
Richard Lewis, from the University of Queensland’s Institute of Molecular Bioscience, said the findings could pave the way for a new range of applications of morphine for pain relief.
“Opiates have had limiting side effects that have basically limited the true potential of this otherwise fantastic analgesic,” Professor Lewis said.
Reducing or eliminating those side effects could lead to major advances in patient and palliative care, he said.
Jessie Richardson contributed to this report.