Age-related decrease of plasma testosterone in SAMP8 mice: replacement improves age-related impairment of learning and memory.

J F Flood; S A Farr; F E Kaiser; M La Regina; J E Morley

doi:10.1016/0031-9384(94)00318-1

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Age-related decrease of plasma testosterone in SAMP8 mice: replacement improves age-related impairment of learning and memory.

J F Flood·S A Farr·F E Kaiser·M La Regina·J E Morley

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Abstract

Corticosterone increases with aging but pregnenolone, dehydroepiandrosterone, and testosterone decrease. The marked decrease in hormones that occurs with aging may contribute to the age-related deficit in learning and memory. Administration of these hormones after training was found to improve long-term memory processing in normal young mice. SAMP8 (P8) mice show an age-related loss of learning and memory for a variety of tasks whereas age-matched control mice of the closely related SAMR1 (R1) strain do not. In this study, we found an age-related decrease in serum testosterone levels of 71% between P8 mice 4 and 12 months of age, but only a 26% decrease between R1 mice of the same ages. The difference between the P8 mice was significant (p < 0.01) and the difference between the R1 mice was not. The decrease in testosterone in 12-month-old P8 mice was not accompanied by gross morphological change in the testes. A SC testosterone implant, sufficient to increase plasma testosterone levels to 414 +/- 25 ng/dl, alleviated impaired learning and memory of a foot shock avoidance task in P8 mice. Castration of 4-month-old P8 mice did not produce a deterioration in learning and memory, indicating that low levels of testosterone per se are not responsible for the impairment seen in 12-month-old P8 mice. This suggests that impaired cognitive functioning of the older P8 mice was due to an interaction of aging and reduced testosterone levels.

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Aging Animals Avoidance Learning Drug Implants Learning Male Memory Mice Mice, Inbred Strains Orchiectomy Species Specificity Testis Testosterone Journal Article Research Support, U.S. Gov't, Non-P.H.S.Research Support, U.S. Gov't, P.H.S.

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J F Flood, S A Farr, F E Kaiser, M La Regina, J E Morley. 1995. Age-related decrease of plasma testosterone in SAMP8 mice: replacement improves age-related impairment of learning and memory.. https://doi.org/10.1016/0031-9384(94)00318-1

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