Whole body vibration ameliorates anxiety-like behavior and memory functions in 30 months old senescent male rats

Abstract

Whole body vibration (WBV) is a form of passive exercise that offers an alternative physical training to aged individuals with limitations in their physical and mental capabilities. The aim of the present study was to explore the therapeutic potential of five weeks of WBV on anxiety-like behaviors as well as learning and memory abilities in senescent thirty months old rats. Animals were exposed to 5 min vibration twice per day, five times per week during the five consecutive weeks. Pseudo WBV treated animals served as controls. After five weeks of WBV treatment, animals were tested for anxiety-like behavior by the open field test and for spatial and object memory functions by the novel and spatial object recognition tests, respectively. As a result, anxiety-like and exploratory behaviors were significantly improved in the WBV treated group compared to the pseudo WBV group. Furthermore, WBV treatment increased discrimination performance in both spatial and object memory function testing. These results indicate that WBV treatment in thirty months old rats seems to have comparable beneficial effects on age-related emotional and cognitive performance as what has been reported in younger age groups.

Keywords: Advanced aging; Open field activities; Passive exercise; Spatial and novel object recognition.

Fig. 1

Experimental flowchart diagram. Male Wistar rats were maintained in the animal facility for 30 months before the Whole Body Vibration (WBV) or pseudo WBV intervention. Animals started the WBV intervention at the age of 30 months and were tested for anxiety-like behavior and memory functions. Main selection and exlusion criterias are mentioned at each steps of the study.

Fig. 2

Experimental design. Thirty months old male Wistar rats underwent a long-term (5 weeks) Whole Body Vibration (WBV) or pseudo WBV intervention involved twice daily exposure of 5 min. After 5 weeks, only morning test procedures were conducted to evaluate anxiety-like behavior and memory functions. The used Marodyne plate is depicted on the left side.

Fig. 3

Open field (OFT) and Novel (NOR) and Spatial (SOR) Object recognition test battery. OFT was conducted to assess unprompted locomotor activity and anxiety-like behavior (Panel A). The frequency of line crossing and rearing was analyzed separately for the inner and outer zones of the area. In addition, latency to exploration, time spent with grooming and frequency of defecation were determined as secondary outcome variables. Object and spatial memory were evaluated through NOR and SOR test series (Panel B). The frequency of object exploration and preference index were determined as outcomes measures. Preference index was calculated as the proportion of exploration frequency at the novel or relocated object to total exploration frequency.

Fig. 4

Horizontal and vertical activity in the OFT. Outcome parameters included horizontal mobility: total line crossing (Panel A), inner zone line crossing (Panel B) and outer zone line crossing (Panel C); and vertical activity: total rearing (Panel D), unsupported (panel E) and supported rearing (Panel F). Data are depicted as mean ± SEM. *p < 0.05 and **p < 0.01.

Fig. 5

Novel and spatial object memory performance in novel object (NOR) and location (SOR) recognition tests. Outcome parameters were determined as NOR: frequency of familiar (Panel A) and novel (Panel B) object exploration, and preference index (Panel C); and SOR: frequency of familiar (Panel D) and replaced (Panel E) object exploration and preference index (Panel F). Data are depicted as mean ± SEM. *p < 0.05 and **p < 0.01.