Purpose: To examine the impact of stress-induced corticosterone (CORT) on cognitive function and lean tissue mass (LTM) in aging.
Subjects: Female F1 Hybrid (Fisher 344 x Brown Norway) rats aged 4-6 months (adult controls, n=4), 22-25 months (young old, n=10) and 27-30 months (old, n=10) were used.
Methods: To measure cognitive performance, directional heading error (DHE) on the Morris water maze was recorded in each animal during 4 trials per day, 8 days pre and post-stress. LTM was estimated using bioelectrical impedance analysis immediately pre and one week post-stress. CORT was determined by radioimmunoassay pre-stress and on day 8 post-stress. Duration of stress events increased by 5 minutes every day for 8 post-stress days.
Results: CORT levels pre-stress, designated as low or high, were significantly different (low=311.3 ± 134.7 g/dl, n=11; high=600.6 ± 133.2 g/dl, n=13; t=-5.29, p < 0.001). Pre-stress mean CORT was significantly lower than post-stress mean CORT (455 ± 197.5 g/dl vs. 1376 ± 482.3 g/dl, n=24; t=-9.946, p<0.001). Rats with high pre and post-stress CORT showed no improvement in DHE until the fourth day after stress events. Rats with low CORT demonstrated no effect of stress on cognition. Difference in learning between groups was not significant. High CORT post-stress was associated with greater loss of LTM (r=1.000, p < 0.001, n=13). There was no association between age, CORT or DHE post-stress (r=0.36, p < 0.05, n=24).
Conclusions: High CORT in the presence of stress is associated with greater loss of LTM and may be associated with reduced cognitive function, independent of age.
Support Contributed By: CERCF, University of Michigan; CFAR, University of Michigan, NIH P60 AG08808-15
Session #1219 - Poster Session I
The 29th Annual MNRS Research Conference (April 1-4, 2005)