Loss of connexin36 in rat hippocampus and cerebellar cortex in persistent Borna disease virus infection

Neonatal Borna disease virus (BDV) infection of the Lewis rat leads to progressive degeneration of dentate gyrus granule cells, and cerebellar Purkinje neurons. Our aim here was to clarify whether BDV interfered with the formation of electrical synapses, and we, therefore, analysed expression of the neuronal gap junction protein connexin36 (Cx36) in the Lewis rat hippocampal formation, and cerebellar cortex, 4 and 8 weeks after neonatal infection. Semiquantitative RT-PCR, revealed a BDV-dependent decrease in Cx36 mRNA in the hippocampal formation 4 and 8 weeks post-infection (p.i.), and in the cerebellar cortex 8 weeks p.i. Correspondingly, immunofluorescent staining revealed reduced Cx36 immunoreactivity in both dentate gyrus, and ammons horn CA3 region, 4 and 8 weeks post-infection. In the cerebellar cortex, Cx36 immunoreactivity was detected only 8 weeks post-infection in the molecular layer, where it was down regulated by BDV. Our findings demonstrate, for the first time, distinct BDV-dependent reductions in Cx36 mRNA and protein in the rat hippocampal formation and cerebellar cortex, suggesting altered neuronal network properties to be an important feature of persistent viral brain infections.