Memories of pain can come back to hurt

"As we search for the molecular basis of pain, we keep uncovering associations between pain and memory," says researcher Clifford Woolf. "Blocking such associations can provide a new basis for treating pain." The key is controlling the excitation of cells that register memories of pain. In one example, to decrease excitability, patients were given spinal injections of painkillers before prostate surgery. Compared with those not so treated, they experienced less pain while hospitalized and were more active after surgery. The pain reduction lasted as long as nine-and-a-half weeks. "When you think about it, the link makes sense," Woolf points out. "During evolution, animals had to learn to recognize what causes pain and to remember to avoid such things. A one-celled amoeba moves away from too much heat just as a human avoids a hot stove."