Magnetic Resonance Imaging Studies On Rat Epileptic Model

The magnetic resonance imaging (MRI) has been used to study the earlier characteristic changes in the brain of acute and chronic epileptic models of rat.The research work of this dissertation can be divided into three parts:First, bioexponential diffusion of water in rat brain before and after picrotoxin induced epilepsy was reported for the first time based on MRI study at 4.7T. Self-comparison of the same rat (n=3) in the normal condition and after injection of picrotoxin showed that diffusion coefficients of both fast and slow diffusion components of water were reduced. At the same time, the content radio of fast and slow diffused water was increased after inducement of epilepsy. This may be the source of the increase in transverse relaxation time of water in the epileptic rat brain.Second, MRI was applied to study the early asymmetric lesion in rat brain with epilepsy induced by chronic tetanus. MRI showed a clear asymmetric hyperintensity in lateral ventriculus (LV). The enhancement of MRI signal intensity was more obvious in contralateral than ipsilateral LV. The hyperintensity in dorsal contralateral LV was related to the frequency of wet dog shakes (WEDS). The result indicated that when the frequency of WEDS reached a critical value, MRI observable hyperintensity became visualized in the dorsal contrlateral LV.Third, the possible role of the Hippocampus(HPC) -Entorhinal(EC)-medial temporal neocortex(MTNC) neural pathway in epileptogenesis was studied by MRI in vivo. Increments in both of MRI signal intensity and the occurrence of WEDS were more remarkable in HPC experimental rats than in MTNC experimental rats. The results showed that HPC may be an "origin" for epileptogenesis and EC may play a "gating" role in it.