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 syna ptogenesis, The receptor of protein tyrosine phosphatase beta (RPTP beta) i s a chondroitin sulphate proteoglycan which plays an important role in neur al morphogenesis and axon guidance mechanisms. Pilocarpine-treated rats pre sent states epilepticus, which is followed by a seizure-free period (silent ), by a period of spontaneous recurrent seizures (chronic), and the hippoca mpus of these animals exhibits cell loss and mossy fiber sprouting. Thus, t he synthesis of heparan sulphate and chondroitin sulphate and the time cour se of RPTP beta immunoreactivity were studied in the hippocampus and cerebr al cortex during these phases of pilocarpine-induced epilepsy. The results showed decreased synthesis of heparan sulphate during the acute phase and a n increased synthesis of chondroitin sulphate during the silent period in t he cortex and hippocampus. In control rats RPTP beta immunoreactivity was d etected only in glial cells, After 6 h of status epilepticus the RPTP beta immunoreactivity was no longer detectable in the glial cells in both tissue s and intense staining became evident in the matrix, surrounding CA3 and de ntate gyrus and piriform cortex neurones, In the silent and chronic periods RPTP beta immunoreactivity was mainly detected in neuronal somata and fibe rs of neurones of hippocampus and cortex. These changes show a selective va riation of synthesis and expression of glycosaminoglycans and RPTP beta in relation to epilepsy suggesting a molecular interplay between glia and neur ones during seizures. (C) 1999 Elsevier Science Inc.