Enhancement of memories by systemic administration of insulin-like growth factor II.

To treat cognitive disorders in humans, new effective therapies that can be easily delivered systemically are needed. Previous studies showed that a bilateral injection of insulin-like growth factor II (IGF-II) into the dorsal hippocampus of rats or mice enhances fear memories and facilitates fear extinction. Here, we report that, in mice, systemic treatments with IGF-II given before training significantly enhance the retention and persistence of several types of working, short-term and long-term memories, including fear conditioning, object recognition, object placement, social recognition, and spatial reference memory. IGF-II-mediated memory enhancement does not alter memory flexibility or the ability for new learning and also occurs when IGF-II treatment is given in concert with memory retrieval. Thus IGF-II may represent a potentially important and effective treatment for enhancing human cognitive and executive functions.