The Impact of Long-term Chewing Stimulation Alterations on Anxiety and Cognition in Young Mice

The investigated influence of long-term increases and decreases in incisal chewing stimulation on anxiety and cognition were investigated in young adult mice, and the underlying mechanisms were explored in detail. The results indicated that chewing was not associated with any significant differences in body weight, morphological differences in the mandibular and masseter muscle fibers, or the morphology of the cortex and hippocampus. In the open field test and elevated plus maze, less anxiety-related behaviors and higher activity levels were observed in the increase group; lower activity levels were observed in the decrease group. In novel object recognition, there were no significant differences in short-term memory ability between the three groups. In the Morris water maze, mice in the increase group exhibited greater spatial cognitive ability than the decrease group. To explore the mechanisms underlying the observed anxiety changes, the epinephrine (E), norepinephrine (NE), dopamine (DA) and 5-hydroxytryptamine (5-HT) neurotransmitters in the cortex and hippocampus were detected using high performance liquid chromatography. The results revealed that the decrease group exhibited higher NE in the cortex compared to the control and increase groups. The mRNA expression of four genes closely related with cognition (Synapsin I, NR2B, CREB and BDNF) were detected using real-time quantitative PCR, to investigate the mechanisms underlying cognitive changes. The results revealed that the decrease group exhibited lower mRNA expression of cognition-related genes in the cortex and the hippocampus, while the increase group exhibited higher mRNA expression in the hippocampus. Overall, the current findings indicate that long-term incisal chewing stimulation enhancement in young adult mice may decrease anxiety-related behavior and increase activity levels and spatial cognition.