Evaluation Of Behaviors In CD-1Mice

BackgroundAging can change the physiological functions of organism, including outstandingbehavioral alterations, even lead to diseases. Although multi-changes of behaviorsmaybe imply aging, not all the behavioral changes take place on the same time. So it’snecessary to find out a middle-aged model for the study of mechanism of aging-self andaging-related behavioral changes. CD-1mouse, an outbred stock with a highheterogeneity of genes, was chosen to establish this middle-aged model.ObjectiveTo evaluate behavioral changes in middle-aged CD-1mice.Methods12middle-aged (13-month old,6males and6females) and13young (5-month old,7males and6females) CD-1mice were used. Behavioral assessment were conducted inthese mice, including species-typical behaviors (burrowing, nesting and hoarding),sensorimotor behaviors (beam walking and tightrope task), spontaneousexploration(open field), anxiety (open field, elevated plus maze and black–white alley),recognition memory (novel-object recognition, object location recognition, andepisodic-like memory task), spatial learning and memory (Morris water maze).Results①Species-typical behaviors: there was insignificant difference in burrowing and nesting behaviors between the two groups (Ps>0.05). But, the middle-aged miceshowed worse performance than the young mice in the hoarding task (P<0.05).②Sensorimotor behaviors: during beam walking, the balance time in the middle-agedgroup was significantly shorter than that in the young group, which was attributable tothe male mice (Ps<0.05). However, the two groups showed no insignificant differencein the tightrope test (Ps>0.05).③Spontaneous exploration: there was insignificantdifference in the times of crossed lines of the open filed between the two groups(P>0.05).④Anxiety in the anxiety-based tasks: in the open field, there wasinsignificant difference in the latency and peripheral time between the two groups. Inthe elevated plus maze test, the middle-aged female mice showed significantly longerlatency than the young female mice (P<0.05). In the black–white alley test, themiddle-aged mice spent significantly longer time in the black alley than the young mice(P <0.05), which was attributable to the female mice. And, the number of times crossingthe two parts in the middle-aged male mice was significantly fewer than that of theyoung male mice (P <0.05).⑤Spatial learning and memory in the Morris water maze:in the navigation task, the latency and the swimming distance of the middle-aged micewere significantly longer than those of the young mice (Ps<0.05). In the probe trial task,there was insignificant difference of the percentage of time and swimming distance inthe target quadrant between the two groups (Ps>0.05).⑥Recognition memory: in theepisodic-like memory task, the middle-aged mice had lower preferential index ofexploring the displaced ‘‘old familiar’’ object than the young mice (P <0.05). In thelocation recognition task, the middle-aged mice showed the similar performance to theyoung mice in both two choices (Ps>0.05). In the novel object recognition task, themiddle-aged mice performed lower preferential index of exploring the novel object thanthe young mice in the delay10min or24h choices (P <0.05). ConclusionThe13-month-old CD-1mice have shown the changes in species-typical behaviors,sensorimotor behaviors, anxiety-like behaviors, spatial memory and recognitionmemory, especially in the females.