Selective alterations of glycosaminoglycans synthesis and proteoglycan expression in rat cortex and hippocampus in pilocarpine-induced epilepsy

Proteoglycans and glycosaminoglycans are elements of matrix. In the nervous system, glycosaminoglycans modulate neurite outgrowth and are co-receptors for growth factors playing a crucial role in cell differentiation and synaptogenesis. The receptor of protein tyrosine phosphatase β (RPTPβ) is a chondroitin sulphate proteoglycan which plays an important role in neural morphogenesis and axon guidance mechanisms. Pilocarpine-treated rats present status epilepticus, which is followed by a seizure-free period (silent), by a period of spontaneous recurrent seizures (chronic), and the hippocampus of these animals exhibits cell loss and mossy fiber sprouting. Thus, the synthesis of heparan sulphate and chondroitin sulphate and the time course of RPTPβ immunoreactivity were studied in the hippocampus and cerebral cortex during these phases of pilocarpine-induced epilepsy. The results showed decreased synthesis of heparan sulphate during the acute phase and an increased synthesis of chondroitin sulphate during the silent period in the cortex and hippocampus. In control rats RPTPβ immunoreactivity was detected only in glial cells. After 6 h of status epilepticus the RPTPβ immunoreactivity was no longer detectable in the glial cells in both tissues and intense staining became evident in the matrix, surrounding CA3 and dentate gyrus and piriform cortex neurones. In the silent and chronic periods RPTPβ immunoreactivity was mainly detected in neuronal somata and fibers of neurones of hippocampus and cortex. These changes show a selective variation of synthesis and expression of glycosaminoglycans and RPTPβ in relation to epilepsy suggesting a molecular interplay between glia and neurones during seizures.