In a previous report, we mimicked an active and a sedentary-life styles in murine model and tested the effects of age, environment and diet regimes on spatial memory, using Morris water-maze task ( Mendes et al., 2013). Furthermore, loss of molars early in life ( Kawahata et al., 2014) or soft diet consumption ( Fukushima-Nakayama et al., 2017) caused loss impaired hippocampal-dependent recognition memory and induced a lateralized preference of object location in recognition tasks ( Kawahata et al., 2014). In addition, it has been reported that inhibition of adequate masticatory function, due soft-diet feeding, occlusal disharmony or molar losses, affected mice cognitive behavior ( Onozuka et al., 2000 Yamamoto and Hirayama, 2001 Tsutsui et al., 2007 Kubo et al., 2010 Ono et al., 2010 Frota De Almeida et al., 2012 Ekuni et al., 2013 Mendes et al., 2013 Sakatani et al., 2013 Nose-Ishibashi et al., 2014 Utsugi et al., 2014 Pang et al., 2015 Takeda et al., 2016 Aguirre Siancas, 2017).
This type of diet-induced obesity progressively alters cognition and mouse performance in the elevated plus maze (EPM) task ( André et al., 2014). The latter outcome appears to be associated with significant changes in hypothalamic synaptic input organization and gliosis ( Horvath et al., 2010). Mastication seems to contribute to maintain body weight within normal limits, and a soft diet has been associated with obesity in murine model ( Desmarchelier et al., 2013). These measurements may be useful in discussions of anxiety-related tasks. We suggest that long life environmental enrichment reduces the tendency to avoid open/lit spaces (OF) and this is particularly influenced by masticatory activity. Although body weight differences were minimized as age progressed, 18M EE group revealed intragroup significant influence of diet regimens. Independent of diet regime, 6M young mice maintained in an EE where voluntary exercise apparatus is available, revealed significant less body weight than all other groups. Although all groups kept their preference by the peripheral zone, the outcomes were significantly influenced by interactions between environment, age, and diet. The locomotor and exploratory activities in OF task declined with age, and this was particularly evident in 18M HD EE mice.
Animals behavior on the open field (OF) task were recorded by webcam and analyzed with Any Maze software (Stöelting).
Under each diet regimen, half of the individuals were raised in standard cages and the other half in enriched cages. Three different regimens of masticatory activity were used: continuous normal mastication with hard pellets (HD) normal mastication followed by reduced mastication with equal periods of pellets followed by soft powder – HD/SD or rehabilitated masticatory activity with equal periods of HD, followed by powder, followed by pellets – HD/SD/HD). We examined in an open arena, the exploratory and locomotor activities of mature (6-month-old 6M), late mature (12-month-old 12M), and aged (18-month-old 18M) mice, subjected to distinct masticatory regimens and environments. As OF arenas are widely used to measure anxiety-like behavior in rats and mice. In the present report, we tested the hypothesis that age, environment, and masticatory changes may interact and alter exploratory patterns of locomotor activity and mice preferences in an open field (OF) arena. However, no study has tested the effects on new environments exploration and risk assessment coupled with a combination of masticatory function rehabilitation and environmental enrichment. Studies indicate that inhibition of adequate masticatory function, due to soft diet, occlusal disharmony, or molar losses affects the cognitive behavior of rodents.