They found that a protein called GRK2 binds to and prevents delta opioid receptors on rat sensory neurons from responding normally to opioids, but when these peripheral neurons were exposed to a natural inflammatory molecule
called bradykinin, GRK2 moved away from the delta opioid receptors, setting off a biochemical reaction that restored the functioning of these receptors.
Then he turned his attention to a synthetic analogue of
bradykinin,
called RMP - 7, that allowed 10 times more chemotherapy to be delivered to the tumor during the 20 - minute window that the blood - brain barrier was open.