Protective Effect Of Apotosis-inhibitory Agent,TPCK,against Kainate-induced Hippocampal CA3 Subfield Neuronal Damage

Objective: 1 .To quantificationally study the relationnship between epileptiform activity and cell death in the CA3 subfield of hippocampus following focally evoked limbic seizures. 2. To study the protective effect of TPCK against kainate-induced hippocampal neuronal damage. 3. To study the probably antiepileptic effect of TPCK(N-tosyl-l-phenylalanyl chloromethy ketone) against kainate-induced seizures of rats. Methods: 1. Animals received intra-amygdaloid injection of kainic acid (KA) to induce type IV epileptiform activity for different duration during continuous electroencephalographic (EEG) monitoring. 72 hour later, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) was used to detect apoptosis cells. The number of surviving CA3 neurons and TUNEL-positive cells were counted, while the number of necrosis cells was estimated. 2. Animals were received intra-amygdaloid injection of kainate (KA) to induce epilepsy and killed 72 hour later. TUNEL was used to detect apoptosis cells. The number of surviving CA3 neurons and TUNEL-positive cells were counted. The difference between therapeutic group and control group were compared. 3. Animals were received intra-amygdaloid injection of kainate (KA) to induce epilepsy. 4 weeks later. seizure frequency was determined by direct observation for 10 hours per week. The difference between therapeutic group and control group were compared. Results: 1. 72 hours after seizures induced by KA injection, the number of necrosis cells was twice as much as that of apoptosis cells in CA3 subfield of hippocampus. The longer the type IV epileptiform activity lasted, the less the neurons were survived. On the contrary, both the number of necrosis cells and apoptosis cells were increased. 2. The number of surviving CA3 neurons was increased and the number of TUNEL-positive cells was decreased in therapeutic groups dose-dependently. 3. In the same period of observation. -3- the number of seizures has no significant difference between therapeutic group and control group (P<0.1). Conclusions: 1. Although the necrosis is induced by epileptiform activity, the apoptosis is the main form of the cell death in CA3 subfield of hippocampus following focally evoked limbic seizures. Increasing the duration of type IV seizures increased numbers of apoptosis cells and necrosis cells. 2. TPCK can protect against kainate-induced hipocampal neuronal damage by its apoptosis inhibitory effect. 3. In the period of observation. TPCK can not reduce the number of seizures of kainate-induced epilepsy model of rats.