PROTEIN LINK TO ADDICTS' CRAVINGS Scientists are paving the way for medicines that could help remove cravings in drug addicts and improve the education prospects of people with learning difficulties. They believe that similar molecular changes in the brain help cause cocaine addiction and impair learning and memory processes. Experiments in mice over the past six years suggest that the absence of a protein called PSD-95 is responsible for both conditions. Researchers at Edinburgh University, the Wellcome Trust Sanger Institute at Hinxton, Cambridgeshire, and Duke University, North Carolina, report the "previously unappreciated" link in the journal Neuron. Work at Edinburgh had already suggested that removing the protein from mice severely limited their ability to learn, apparently because it interfered with the way brain synapses changed electrical activity in nerve cells into chemical activity. Work in the US exposing mice to cocaine reduced levels of the protein in parts of the brain linked to movement and emotional response. Drug addicts often have problems with memory and coordination, but scientists now believe they know why: they are suffering molecular brain damage. Seth Grant, professor of molecular neuroscience at Edinburgh, said: "The protein molecule is important in the type of learning to do with people, places and things, so cocaine strikes at the kinds of learning which would include, for example, studying for examinations." Addiction and learning were repetitive processes, he suggested. The research should make it possible to begin investigating drugs that might reverse the damage, said Prof Grant. They might help drug abusers and people with disorders such as schizophrenia and those with learning difficulties. But he advised caution in developing drugs to enhance the learning capabilities of healthy people by interfering with fundamental molecular mechanisms. "I would be very concerned that that might lead to psychiatric disorder," he said.