Researchers at the University of Puerto Rico, School of Medicine have found a way to pharmacologically induce a memory of safety in the brain of rats. As reported in the June, 4 2010 issue of Science, administering brain-derived neurotrophic factor (BDNF) into the prefrontal cortex prevented rats from expressing fear to a tone that had been previously paired with a shock. Rats given BDNF acted as if they had received repeated presentations of the tone without the shock, a procedure called extinction. "The surprising finding here is that the drug substituted for extinction training, suggesting that it induced a memory for extinction", said Dr. Gregory Quirk of the Department of Psychiatry, who led the investigation. This finding could suggest new treatments for individuals suffering from anxiety disorders. In this video, laboratory rats listening to a tone (indicated by light on bottom right) that had been paired with shock. Control rats froze with fear but rats injected with brain-derived neurotrophic factor (BDNF) were not afraid, continuing to press a bar for food. Credit: Dr. Gregory Quirk, Univ. Puerto Rico