Objective: 

Depending on the type and duration, stress affects cognitive functions. It is known that acute stress improves cognitive function in adults, but it is unknown how it affects in adolescents. The purpose of this study is to study the effects of low and high intensity of acute stress in hippocampus in the adolescent period.

Methods: 

Groups: both sexes, high intensity (1.6 mA) and low intensity (0.2 mA) stress groups and controls. Learning and memory performances were evaluated using Morris water tank, after 1 hour, 20 minute foot shock stress. VEGF and BDNF levels were measured by ELISA. Also, VEGF immune staining was performed.

Results: 

Stress affected learning processes significantly in all groups. In probe trial, the stressed groups had more time in target quadrant, had less time in opposite quadrant (p <0.003, p <0.004). Increased the cell number in CA1 and gyrus dentatus, increased VEGF and BDNF levels of hippocampus (p <0.05). Also, VEGF + cells were determined by VEGF immune staining. Gyrus dentatus and CA1 cell counts, levels of VEGF and BDNF were positive correlated with time spent in target quadrant (r=0.548, p=0.001; r=0.341, p=0.042; r=0.423, p=0.020; r=0.438, p=0.016), were negative correlated with time spent in opposite quadrant (r=-0.643, p=0.000; r=-0.455, p=0.005; r=-0.376, p=0.040; r=-0.388, p=0.034). There was no difference between basal corticosterone levels in all groups.

Conclusions: 

These results suggest that of low and high intensity of acute stress showed similar positive effect on hippocampus in the adolescents, whose hypothalamus-pituitary-adrenal axis were not in the adult form yet.