DISTRIBUTION AND LEVELS OF INSULIN-LIKE-GROWTH-FACTOR-I MESSENGER-RNAACROSS THE LIFE-SPAN IN THE BROWN-NORWAY X FISCHER-344 RAT-BRAIN

Previous studies have reported changes in insulin-like growth factor I (IGF-I) mRNA expression during early postnatal development of the rat brain. Although changes in IGF-I gene expression have been documented in a wide range of central nervous system structures during early deve lopment and investigated in the hippocampus during aging, no study has compared changes in IGF-I gene expression in different brain regions across the Life span. The present study assessed the distribution of I GF-I gene expression using in situ hybridization in rats aged 2-30 mon ths. Dot blots were used as a quantitative assessment of cortical IGF- I mRNA. Results indicate that both the distribution and levels of brai n IGF-I mRNA do not change significantly between 2 and 30 months of ag e in the rat. However, in spite of relatively constant levels of mRNA, other studies from our laboratory have demonstrated that cortical IGF -I protein levels decrease 36.6% between 11 and 32 months of age, sugg esting that IGF-I function is decreased with increasing age. (C) 1998 Elsevier Science B.V. All rights reserved.