Activation of Sphingosine 1-Phosphate Receptor 1 Enhances Hippocampus Neurogenesis in a Rat Model of Traumatic Brain Injury: An Involvement of MEK/Erk Signaling Pathway
Cognitive function of rats in sham, TBI+Vehicle, TBI+SEW, TBI+SEW+U0126, TBI+VPC, and TBI+VPC+ERN group ( in sham and in other groups) were evaluated by Morris water maze (MWM) test. (a) Escape latency in hidden platform trial exhibited a gradual reduction tendency from 24 to 27 days after trauma. Daily escape latency of TBI+Vehicle group was longer than that of sham group. Use of S1PR1 agonist in TBI+SEW group significantly shorten the latency, but the effect was eliminated in TBI+SEW+U0126 group. In addition, the escape latency of TBI+VPC+ERN group decreased compared with TBI+VPC group. (b, c) Platform crossing times and target quadrant duration in probe trial revealed that, relative to sham group, TBI+Vehicle group presented less times and shorter duration at 28 days after TBI. S1PR1 activation significantly increased the two indexes of TBI+SEW group, but the favorable effect was blocked by U0126 treatment in TBI+SEW+U0126 group. Moreover, the times of platform crossing and duration in target quadrant of TBI+VPC group were lower than those of TBI+VPC+ERN group. (d) Rat swimming speed of the six groups did not show any statistical difference. versus sham group; versus TBI+SEW group, versus TBI+VPC group.