EXPRESSION OF BDNF AND TRKB AS A FUNCTION OF AGE AND COGNITIVE PERFORMANCE

The expression of the neurotrophic factor BDNF increases during learni ng-related events and is decreased in the hippocampus of Alzheimer's D isease patients, suggesting that it plays a role in learning, memory, and/or age-related memory deficits. We examined the expression of BDNF and its high affinity receptor, trkB, in young and aged Sprague-Dawle y rats. BDNF and trkB mRNA were measured by semi-quantitative in situ hybridization and BDNF protein was measured by ELISA. Significant decr eases with age were detected for BDNF mRNA in the pens, BDNF protein i n the midbrain, and trkB mRNA in many areas of the brain. Rats were ev aluated on the Morris water maze before sacrifice so that BDNF and trk B levels could be related to cognitive status. Regression analyses rev ealed that decreased trkB mRNA in the pons significantly predicted imp aired memory performance in aged rats. These results suggest that decr eases in trkB mRNA with age are more widespread than decreases in BDNF , and that BDNF decreases are restricted to more caudal brain regions. (C) 1998 Elsevier Science B.V. All rights reserved.