Expressions of cAMP response element binding protein and phosphorylated cAMP response element binding protein in the hippocampus of drug resistant temporal lobe epileptic rats

Abstract

Objective To establish drug resistant models of temporal lobe epilepsy induced by amygdala kindling, and to investigate the changes of cAMP response element binding protein (CREB) and phosphorylated cAMP response element binding protein (p-CREB) expression in the hippocampus tissues in order to explore their roles in drug resistant epileptogenesis. Methods Eighty adult male SD rats were randomly divided into control group (n=10) and model group (n=70). The 70 rats were used to prepare the amygdaloid kindled model of epilepsy by chronic stimulation of amygaloid basal lateral nucleus. The successful kindled models were randomly selected as drug resistant epileptic group (n=10) and drug sensitive epileptic group (n=10) according to their response to the phenytoin and phenobarbital. On the basis of behavioral observation, electrophysiology, pathological HE staining, CREB and p-CREB expression changes, we verified the reliability of the models and explored the differences among the three groups above. The changes of CREB and p-CREB expression were detected by immunohistochemical method and Western blotting assay. Results In control group, the electroencephalogram (EEG) frequency was (8.700±1.494) Hz; in drug sensitive epileptic group, the EEG frequency was (14.700±1.159) Hz; in drug resistant epileptic group, the EEG frequency was (19.800±1.686) Hz. The frequency differences among the three groups were statistically significant (F=144.202, P=0.000). By immunohistochemical staining, a large number of CREB and p-CREB positive cells were observed in drug resistant epileptic group. As compared with the control group (CREB 0.197±0.058, p-CREB 0.260±0.176), the expression levels of CREB and p-CREB were increased in drug sensitive epileptic group (CREB 0.361±0.151, p-CREB 0.656±0.234) and in drug resistant epileptic group (CREB 0.591±0.150, p-CREB 1.077±0.400). The difference among the three groups had statistical significance (F=24.206, 20.376, both P<0.01). Conclusions The expressions of CREB and p-CREB were significantly increased in drug resistant epileptic rats. These findings indicate that the expressions of CREB and p-CREB may play certain roles in the drug-resistant epileptogenesis. Key words: cAMP response element binding protein; Phosphorylated cAMP response element binding protein; Drug resistance; Epilepsy; Hippocampus