Voluntary wheel running: patterns and physiological effects in mice

Exercise can prevent and improve the pathophysiology of diseases and promote healthy aging. Thus, understanding the mechanisms that regulate the beneficial effects of exercise may lead to the development of new strategies to enhance quality of life and to counteract chronic diseases. Voluntary wheel running is an interesting model to study the effects of exercise in mice. Compared to forced treadmill exercise, voluntary wheel running presents several advantages such as: 1) running pattern is similar to natural running behavior of mice; 2) it is performed under non-stressed conditions, according to the rhythmicity of the animal; 3) it does not require direct interference from the researcher, and can be easily applied in long-term studies. Mice run spontaneously when given access to running wheels, for a total distance of ∼4 to 20 km per day and a total activity time of ∼3 to 7 hours a day. Hence, voluntary wheel running can result in robust endurance-like adaptation in skeletal and cardiac muscles and protect from sarcopenia. However, due to the lack of control over exercise parameters in voluntary exercise models, it is important for the researcher to understand the patterns and variability of wheel running in mice, as well as the factors that can affect voluntary running activity. Overall, voluntary wheel running in mice is a very interesting approach to study the chronic adaptation to exercise, analyze the effects of exercise, and test exercise capacity in different experimental models.

Effects of acute and chronic physical exercise and stress on different types of memory in rats

Here we study the effect of acute and chronic physical exercise in a treadmill and of daily stress (because forced exercise involves a degree of stress) during 2 or 8 weeks on different types of memory in male Wistar rats. The memory tests employed were: habituation in an open field, object recognition and spatial learning in the Morris water maze. Daily foot-shock stress enhanced habituation learning after 2 but not after 8 weeks; it hindered both short- (STM) and long-term memory (LTM) of the recognition task at 2 weeks but only STM after 8 weeks and had no effect on spatial learning after either 2 or 8 weeks. Acute but not chronic exercise also enhanced habituation in the open field and hindered STM and LTM in the recognition task. Chronic exercise enhanced one important measure of spatial learning (latency to escape) but not others. Our findings indicate that some care must be taken when interpreting effects of forced exercise on brain parameters since at least part of them may be due to the stress inherent to the training procedure.

Neste trabalho estudamos os efeitos do exercício forçado diário em esteira rolante e da exposição diária ao estresse (porque o exercício forçado envolve um certo grau de estresse) durante 2 ou 8 semanas em diferentes tipos de memória em ratos Wistar machos. Os testes de memória utilizados foram: habituação da exploração em um campo aberto, reconhecimento de objetos, e memória espacial no labirinto aquático de Morris. O estresse diário facilitou a memória de habituação, os animais aprenderam após 2 mas não após 8 semanas; houve prejuízo na memória curta (STM) e de longa duração (LTM) no teste de reconhecimento em 2 semanas, mas somente de STM após 8 semanas; não houve nenhum efeito na memória espacial após 2 ou 8 semanas. O protocolo do exercício facilitou também a memória de habituação no campo aberto após 2 mas não após 8 semanas; prejudicou STM e LTM na tarefa do reconhecimento após 2 mas não após 8 semanas; e facilitou uma medida importante da aprendizagem espacial após 8 semanas (latência de escape), mas não outras medidas. Nossos resultados indicam que algum cuidado deve ser tomado ao se interpretar efeitos de exercício forçado sobre as funções cognitivas, já que uma parte deles, embora não todos, podem ser atribuídos ao estresse inerente ao exercício.