Insulin-like growth factor-1 ameliorates age-related behavioral deficits

Insulin-like growth factor-1 has been found to be involved in the regulation of several aspects of brain metabolism, neural transmission, neural growth and differentiation. Because decreased insulin-like growth factor-1 and/or its receptors are likely to contribute to age-related abnormalities in behavior, the strategy of replacing this protein is one potential therapeutic alternative. The present study was designed to assess whether cognitive deficits with ageing may be partially overcome by increasing the availability of insulin-like growth factor-1 in the brain. Fischer-344 x Brown Norway hybrid (F1) male rats of two ages (four-months-old and 32-months-old) were preoperatively trained in behavioral tasks and subsequently implanted with osmotic minipumps to infuse the insulin-like growth factor-1 (23.5 microg/pump) or a vehicle, i.c.v. Animals were retested at two weeks and four weeks after surgery. Insulin-like growth factor-1 improved working memory in the repeated acquisition task and in the object recognition task. An improvement was also observed in the place discrimination task, which assesses reference memory. Insulin-like growth factor-1 had no effect on sensorimotor skills nor exploration, but mildly reversed some age-related deficits in emotionality. These data indicate a potentially important role for insulin-like growth factor-1 in the reversal of age-related behavioral impairments in rodents.