A Preliminary Study On Effects Of Sciatic Nerve Stimulation On The Propagation Of Cortical Spreading Depression

So far, many techniques have been used to study cortical spreading depression (CSD), including electrophysiological methods, histochemistry and functional magnetic resonance imaging (fMRI). Optical intrinsic signal imaging (OISI) provides high temporal (tens of millisecond) and spatial (microns) resolution to map brain function through measuring the optical reflectance of the cortex. It is a powerful tool in studying the characteristics of the spatiotemporal evolution of CSD waves. To investigate the relationship between the optical intrinsic signal (OIS) and the electrophysiologic activity and the mechanism of neural-vascular coupling during CSD, it is needed to simultaneously record the changes in OIS and electrophysiologic activity.Based on the virtual instrument technology, a synchronizing module was developed to combine the optical intrinsic imaging system with extracellular electrophysiologic signal recording instruments so that the OIS and neural electrical activity can be recorded simultaneously. Furthermore, a multi-parameters electrophysiologic stimulator and a stimulation isolator were also developed to provide the electrical stimulation to the experimental animals. The synchronization between the stimulator, OIS recording and electrophysiologic activity recording was realized.Using this optical imaging system, we investigated the effects of sciatic stimulation on the propagation of cortical spreading depression. In the experiments, we found that the spreading velocity of CSD declined from 3.630±0.272 mm/min to 3.060±0.260 mm/min during the sciatic nerve stimulation, comparing with that without sciatic nerve stimulation. Besides, we carried on the primary studies on the method of the CSD induction produced by cortical electrical stimulation, and the effect of stimulation time interval on the spreading pattern of the CSD waves. The experimental results suggest that electrical stimulation pulse which can induce CSD should have the product of the pulse width and the current intensity larger than 0.5 mA?S. In addition, it was showed that the spatial spreading of the CSD was partially developed as the stimulation interval was shorter than 250 s.