The Expression Of Pannexin-1mRNA And Connexion36mRNA In Temporal Lobe Cortex And Hippocampus And The Interventi-onal Effect Of Carbenoxoone In The Kindling Rats By Pentylenetetrazole

1 Background and objectiveEpilepsy is a kind of chronic cerebral disease characterized by repetitive paroxysmal and transient central nervous system. (CNS) dysfunction caused by abnormal discharge of neurons. Although the pathogenesis of epilepsy is complex, the essence is the excessive synchronous discharge of cerebral cortex neurons.Recent research indicated that this discharge is closely related with ion channel, neurotransmitter, neuroglia cells, synaptic transmission, and gap junction. At present, gap junction is one of the hot spots. Gap junction is a type of channel for substance information exchange directly, which is the basic structure of electrical synapse, and prompted synchronized activities of vicinal cells causing paradoxical discharge. Gap-junction protein is the infrastructure of gap junction. At present, at lest twenty kinds of connexion gene and three kind of panexin gene had been found encode junction protein of rats in abroad. Cx36 (connexion-36) had high expression in central nervous system. However, the research of PX1 (pannexin-1) is hardly seen in China. Carbenoxolone which was used to cure peptic ulcer originally can permeate blood-brain barrier well and block up the gap junction, as well as had been found restraint epileptiform discharge in vitro experiment. By pentylenetetrazole kindling rat model, this study observed the expression of PX1mRNA and Cx36mRNA in hippocampus and temporal lobes and the intervention of carbenoxolone (CBX).2 Materials and MethodsThirty healthy adult male SD (Sprague-Dawley) rats were randomly divided into three groups:PTZ-kindled(K) group, CBX group, normal saline(NS) group,10 in each group. K group and CBX group were firstly given PTZ 35mg/(kg. d) by intraperitoneal injection to establish the epilepsy model. After kindling successfully, the groups were respectively injected NS and CBX 10mg/kg for three days in abdominal cavity as intervention. At the same time, the NS group were given NS 3.5mL/(kg/d) only by intraperitoneal injection. The injection solution had been given to the three groups once a day at the fixed time.According to the Racine scale of seizure activity,the behavior of all rats were observed and recorded after injection daily. When the seizure activity of experimental rats reached kindling criterion and had been intervened for three days, the brains were taken out by decapitation at the same time. The expression of PX1mRNA and Cx36mRNA in temporal lobe cortex and hippocampus were detected by RT-PCR. The data were expressed by mean±standard deviation(X±S) and analyzed with spss 13.0 statistical software. One-way ANOVA test were used in comparison among groups. The significant level is a=0.05.3 Results(1) At the first two weeks, K and CBX groups had seizure of classⅠ-Ⅱ.Most seizure were happened ten to fifteen minute after intraperitoneal injection, rarely thirty minutes later. At the forth week, all of the rats had seizure of classⅣ-Ⅴand reached total kindling criterion, except the NS group which didn't have seizure. After kindling, the K group had major seizure ofⅠ-Ⅲ, seldomⅣandⅤ. The CBX group had seizure ofⅠ-Ⅱ, rarelyⅢ-Ⅴ.(2) In the hippocampus and temporal lobe, the expression of PX1mRNA and Cx36mRNA in the K group and CBX group is higher than in the NS group (P<0.01), and the expression in the K group is higher than in the CBX group (P<0.05). Whereas, in the three groups, the expression of PX1mRNA in the hippocampus is higher than in the temporal lobe (P<0.05), at the same time, the expression of Cx36mRNA in the temporal lobe is higher than in the hippocampus (P<0.05).4 Conclusion(1) In the aspect of animal behavior, PTZ can induce the seizure of rat, which simulated the generation and process of mankind chronic epilepsy.(2) CBX intervention can reduce the spontaneous seizure degree and duration of kindling rats.(3) The high expression of PX1 mRNA and Cx36mRNA in the temporal lobe and hippocampus of chronic kindled rats indicated that gap junction protein PX1 and Cx36 may involve in the pathogenesis of epilepsy.(4) PX1mRNA has higher expression in hippocampus than in temporal lobe. Whereas, Cx36mRNA has higher expression in temporal lobe.(5) CBX made the expression of gap junction PX1 and Cx36 higher than the NS group. Though the pathogenesis is unknown, CBX had potential effort of anti-convulsion or assistant anti-convulsion.