Evidence that ames dwarf mice age differently from their normal siblings in behavioral and learning and memory parameters

There is strong evidence supporting the deleterious effects of aging on lea rning and memory and behavioral parameters in normal mice. However, little is known about the Ames dwarf: mouse, which has a Prop-1 gene mutation resu lting in deficiencies in growth hormone, thyroid-stimulating hormone, and p rolactin. These mice are much smaller and live significantly longer than th eir normal siblings. Using the elevated plus-maze, locomotor activity meter s, and an inhibitory avoidance learning task, the present study compared Am es dwarf mice to their normal siblings. Results showed that Ames dwarf mice did not experience an age-related decline in locomotor activity when compa red to their young counterparts. Furthermore, old dwarf mice did not differ from the young groups in inhibitory avoidance retention, while old normal animals performed more poorly than both young groups on this test. Elevated plus-maze behavior did not differ in the old normal versus dwarf groups, b ut the old groups did differ from the young. Results indicate that both old groups experienced a significant decline in anxiety with age. Taken togeth er, these results indicate that multiple hormone deficiencies resulting fro m a lack of primary pituitary function have beneficial effects on cognitive function and locomotor behavior in advanced age. In fact, the Ames dwarf m ouse may provide a model for studies of delayed mental as well as physical aging. (C) 2001 Academic Press.