The synthesis and distribution of the kinin B1 and B2 receptors are modified in the hippocampus of rats submitted to pilocarpine model of epilepsy

Abstract

Kinins, a special class of polypeptides, are represented by bradykinin (BK), kallidin (Lys-BK), as well as their metabolites. The biological actions of these polypeptides binding on their receptors (B1 and B2) have been related to inflammation process, cytokines action, glutamate release and prostaglandins production. Usually, kinin B1 receptor is not expressed at a significant level under physiologic conditions in most tissues, but its expression is induced by injury, or upon exposure in vivo or in vitro to pro-inflammatory mediators. The kinin B2 receptor subtype is constitutively and widely expressed throughout the central and peripheral nervous system. These data raise the possibility for de novo expression of those receptors during the temporal lobe epilepsy (TLE), which has been related to cell death, gliosis and hippocampal reorganization. To correlate kinin system and TLE, adult male Wistar rats were submitted to pilocarpine model of epilepsy. The hippocampi were removed 6 h, 5 and 60 days after status epilepticus (SE) onset. The collected tissues were used to study the expression of kinin B1 and B2 mRNA receptors, using Real-Time PCR. Immunohistochemistry assay was also employed to visualize kinin B1 and B2 distribution in the hippocampus. The results show increased kinin B1 and B2 mRNA levels during acute, silent and chronic periods and changes in the kinin B1 and B2 receptors distribution. In addition, the immunoreactivity against kinin B1 receptor was increased mainly during the silent period, where neuron clusters of could be visualized. The kinin B2 receptor immunoreactivity also showed augmentation but mainly during the acute and silent periods. Our results suggest that kinin B1 and B2 receptors play an important role in the epileptic phenomena.