Upregulation of Connexins 30 and 32 Gap Junctions in Rat Hippocampus at Transcription Level by Chronic Central Injection of Lipopolysaccharide

Gap junctions composed of connexins (Cx) are functional in cell defense by propagation of toxic/death molecules to neighboring cells. Hippocampus, one of the brain regions with particular vulnerability to damage, has a wide network of gap junctions. Functional response of astrocytic Cx30 and neuronal Cx32 to hippocampal damage is unknown. We infused lipopolysaccharide (LPS) intracerebroventricularly (2.5 µg/rat) once daily for two weeks to create neuroinflammation. The mRNA and protein levels of the Cx were measured in the hippocampus after 1st, 7th and 14th injection by real-time PCR and Western-blot techniques. A significant increase in Cx32 and Cx30 gene expression was observed after 7th and 14th injection of LPS with no significant change in their protein abundance. Transcriptional overexpression of hippocampal Cx30 and Cx32 could be an adaptive response to production of intracellular toxic molecules but it is not accompanied with post- transcriptional overexpression and might have no functional impact.