Expression of connexin genes in hippocampus of kainate-treated and kindledrats under conditions of experimental epilepsy

We have analyzed whether the expression of connexin genes is altered in the hippocampus of kindled and kainate-treated rats, i.e., animal models of hu man temporal lobe: epilepsy. We have tested this hypothesis by analyzing mR NA, protein abundance and cellular Location of connexins (Cx) 43, 36, 32 an d 30. The expression of glial fibrillary acid protein and mRNA was also mon itored both in kainate-treated and kindled rats, in order to take into acco unt reactive gliosis under these conditions. We found significantly increas ed expression of GFAP mRNA (100%) and protein (178%) in kainate-treated rat s 4 weeks after kainate application, whereas in kindled rats only moderate increases of GFAP mRNA and protein were detected 2-3 weeks (group 2) or 4-G weeks (group 1) after the last stage 5 induced seizure. Under gliotic cond itions, connexins 33 and 30 mRNA or protein expression in astrocytes of kai nate-treated rats were nearly unaffected. Cx36 mRNA expression (presumably in neurons) was significantly reduced (44%), whereas abundance of Cx36 prot ein was only slightly reduced. In both groups of kindled rats, Cx30 and Cx4 3 mRNA or protein expression were either slightly decreased or unchanged. A gain, Cx36 mRNA and protein expression were reduced by about half in group 2. Immunofluorescence analysis of Cx43, Cx36 and Cx30 expression revealed t hat 4 weeks after the last kainate administration or kindling, cellular loc alization of these connexins was indistinguishable from control animals. (C ) 2000 Elsevier Science B.V. All rights reserved.