Morphine is one of the most effective pain-relievers that we know of, but it comes at the hefty price of also being horribly addictive. As such, the drug can’t be administered by doctors for long-term pain – the risk of creating a junkie is just too high. But researchers at the University of Adelaide,in Australia, have found that the opioid high from morphine also comes with an immune response from the body. By blocking a particular receptor,called TLR-4,on the cell surface with a separate drug known as plus-naloxone,addictive behavior seems to be nullified. Testing it on rats,the team found that they did not show signs of dependence. Further study could thus lead to drugs with all the benefits of morphine and other opioid compounds – but with none of the hazards.