[Effects of Synaptotagmin1 gene knockout on the behavior of mice]

Objective: To study the effects of Synaptotagmin1 gene knockout (Syt1^+/-) on emotional behavior in mice and explore its possible mechanisms. Methods: Five 8-week-old male Syt1^+/-mice and five wild-type (WT) mice in the same litter were selected. The expressions of Syt1 in 6 mice brain regions of prelimbic cortex (PL), hippocampus (HIP), amygdala (AMY), accumbens nucleus (ACB), caudoputamen (CP) and ventral tegmental area (VTA) were detected by Immunofluorescence staining. Nine 8-week-old male Syt1^+/-mice and ten WT mice were selected as controls. The anxiety-like behaviors of adult Syt1^+/- mice and WT mice were detected by open field test, elevated plus maze test and forced swim test. In addition, five 8-week-old male Syt1^+/-mice and five WT mice were selected to detect the glutamate content in prelimbic cortex, hippocampus and amygdala. Results: Compared with WT mice, the number of Syt1 positive cells in PL, HIP, AMY, ACB, CP and VTA were decreased significantly in Syt1^+/- mice (P＜0.01); Syt1^+/- mice had less total movement distance in open field test (P＜0.01), more preference for peripheral area (P＜0.01) and less desire to explore the central platform (P＜0.01), while Syt1^+/- mice preferred to stay in a closed and safe environment (P＜0.01); the number (P＜0.05) and the time spent in open-arm explorations (P＜0.01) were reduced significantly; the immobile time of Syt1^+/- mice was increased in the forced swim test (P＜0.01). Meanwhile, the concentration of glutamate in the amygdala of Syt1^+/- mice was increased significantly (P＜0.01). Conclusion: Syt1 gene knockout leads to significant anxiety-like behavior in mice, which is deduced that related to the increase of glutamate content in the amygdala.