The Effects Of Conditioned Fear Stimulus On Stem Cells Proliferation And Differentiation To Neurons In Adult Rat Amygdala

Objective:To investigate the impact of conditioned fear stimulus on the proliferation and differentiation of neural stem cells in rat amygdala.Methods:1. The rat conditioned fear models were built by using monotone matching foot shock. The memory of the conditioned fear stimulus was measured by freezing time.2. The expression of BrdU (the exogenous marker of stem cell) in rat amygdala of different time groups (1,7,14,21,30,60 days) was detected by immunohistochemistry.3. The co-expression of BrdU and NeuN (the marker of neuron) in rat amygdala was detected by immunofluorescence double labeling method.4. SPSS statistical software program (version 15.0, SPSS, Inc.) was used for statistical analysis.Result:1. Behavioral assessment of 1,7,14,21,30,60 days after the conditioned fear stimulus event showed there was significant difference of freezing time between the conditioned fear groups and the control groups within the 8 minutes after they were given the monotone stimulus (P<0.01).2.The BrdU-immunohistochemistry showed there were classic BrdU positive marks in the amygdala of both groups. The number of BrdU positive cells in rat amygdala was significant reduced in conditioned fear groups of 1,7,14,21,30 days after been given the conditioned fear stimulus than that in the corresponding control groups (P<0.05), while there was no significant difference between conditioned fear group of 60 days and the corresponding control group.3.The double labeling of BrdU and NeuN showed there was distinct co-expression of BrdU and NeuN in the amygdala of both groups. The percentage of BrdU and NeuN co-expression positive cells in rat amygdala was significant decreased in conditioned fear groups of 1,7,14,21,30,60 days after been given the conditioned fear stimulus (P<0.05).Conclusion:The freezing time of rats was significantly extended following the conditioned fear stimulus. The conditioned fear stimulus insult can induce the reduction of cells proliferation in rat amygdala, suggesting it maybe influence the neurogenesis in rat amygdala.