Preservation of cognitive and motor function in middle-aged animals: Implications for the role of growth hormone in aging





B.A. Kinney, N.E. Kinney, K.T. Coschigano, J.J. Kopchick, R.W. Steger, A. Bartke

Department of Physiology, Southern Illinois University School of Medicine, Carbondale, IL 62901-6512



Although the role of growth hormone (GH) in aging is controversial, the recent production of GH receptor/GH binding protein knock-out (GH-R-KO) mice may provide a means for elucidating its importance. Previous studies have shown that GH-R-KO mice and GH-deficient dwarf mice both live significantly longer than their normal siblings, clearly establishing the importance of GH for longevity. Efforts are now underway to determine if the GH-R-KO mice experience a parallel delay in age-induced deterioration in neurological function. Using the water maze and activity meters, the present studies aimed at comparing cognitive function and locomotor activity in middle-aged (12-14 mo) GH-R-KO mice and their normal siblings to that of their young (2-4 mo) counterparts. Animals were screened for physical health and any animal displaying difficulty swimming was removed from the study. Average swimming speeds for all groups were determined for separate age-matched animals and were found to be comparable. Water maze results revealed that the middle-aged normal animals learned the task over the 8-day testing period, but that their learning was delayed compared to young normal animals (p < .05). In contrast, middle-aged GH-R-KO mice did not differ from young normal animals or young GH-R-KO animals in water maze performance over all trials. Similar findings were obtained with the activity meters. While middle-aged normal animals were not as spontaneously active as their young counterparts, F(1,39) = 12.48, p < .001, the middle-aged and young GH-R-KO animals did not differ in activity levels, F(1,40) = 2.683, p = .109. Taken together, these results support previous findings suggesting that GH-R-KO mice experience a delay in age-induced cognitive and locomotor deterioration compared to their normal siblings. This work was supported by the Illinois Council for Food and Agricultural Research (C-FAR) and by NIH (AG19899).




Key words: aging, cognition, longevity, behavior, brain







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