Method: Three-week-old C57BL/6 male mice were subjected to molar extraction and received a daily injection of 5-bromo-2’-deoxyuridine (BrdU, 30mg/kg i.p.) for 3 consecutive days in 15weeks. Immunohistochemistry for BrdU and immunofluorescent labeling for NeuN (neuron marker) were performed. Further, we performed OLT in 14 and 21 weeks of their age. In the acquisition phase, mice were exposed to objects A1 and A2, which were placed in the far corners of the arena. The animal was allowed to explore both objects during a sample phase of 5 min. After 24 h, the test phase began in which object A2 was placed in the different position in the sample phase. Thus, both objects in the test phase were equally familiar, but one was in a new location.
Result: The molarless condition decreased BrdU-positive cells in the HDG (p < 0.01).Furthermore, in the test phase trials, exploration times for the solid food group clearly showed a preference for the object placed in a new location compared to the object placed in a familiar location (p < 0.05). In contrast, the animals of the molarless group showed that they were unable to discriminate a novel location from a familiar location.
Conclusion: The molarless condition suggest that reduced the proliferation of newly generated cells in the adult DG in the early stage. And the production of new neurons in the HDG during adulthood may be related to short term memory.