Improvements in health care have greatly increased life span in the United States. The focus is now shifting from physical well-being to improvement in mental well-being or maintenance of cognitive function in old age. It is known that elderly people suffer from cognitive impairment, even without neurodegeneration, as a part of 'normal aging'. This 'age-associated memory impairment' (AAMI), can have a devastating impact on the social and economic life of an individual as well as the society. Scientists have been experimenting to find methods to prevent the memory loss associated with aging. The major factor involved in these experiments is the use of animal models to assess hippocampal-based spatial memory. This review describes the different types of memory including hippocampal-based memory that is vulnerable to aging. A detailed overview of various behavioral paradigms used to assess spatial memory including the T-maze, radial maze, Morris water maze, Barnes maze and others is presented. The review also describes the molecular basis of memory in hippocampus called as 'long-term potentiation'. The advantages and limitations of the behavioral models in assessing memory and the link to the long-term potentiation are discussed. This review should assist investigators in choosing suitable methods to assess spatial memory in mice.

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Summary Growth hormone significantly impacts lifespan in mammals. Mouse longevity is extended when growth hormone (GH) signaling is interrupted but markedly shortened with high plasma hormone levels. Methionine metabolism is enhanced in growth hormone deficiency, e.g. Ames dwarf, but suppressed in GH transgenic mice. Methionine intake affects also lifespan, thus, GH mutant mice and respective wild type littermates were fed 0.16%, 0.43% or 1.3% methionine to evaluate the interaction between hormone status and methionine. All wild type and GH transgenic mice lived longer when fed 0.16% methionine but not when fed higher levels. In contrast, animals without growth hormone signaling due to hormone deficiency or resistance, did not respond to altered levels of methionine in terms of lifespan, body weight or food consumption. Taken together, our results suggest that the presence of growth hormone is necessary to sense dietary methionine changes thus, strongly linking growth and lifespan to amino acid availability.

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