While glial cells are well investigated in the cortex and hippocampus, little is known about their properties and functions in the thalamus. Here we investigated morphological and functional properties of astrocytes and oligodendrocytes in the VPL and VPM nuclei of the thalamus. We combined electrophysiology, immunohistochemistry and 2-photon-imaging with semi-quantitative RT-PCR and Western blot analysis to investigate receptor and connexin expression, gap junction coupling and antigen profiles. Experiments were performed in wild type and transgenic mice. Cells were investigated between postnatal days 8–120.

In freshly isolated astrocytes kainate induced small responses in a subset of the cells while much larger currents were evoked by GABA_A receptor activation. Investigations of cell-cell coupling by biocytin filling of astrocytes of hGFAP-EGFP mice revealed large gap-junctional-networks in young and adult mice which were stable in size during aging. In contrast to findings in the hippocampus, coupling in the thalamus was not decreased in heterozygous Cx43-CFPki mice. In these mice SR101 labeling of astrocytes and subsequent 2P microscopy identified a significant subset of SR101+ cells lacking CFP fluorescence. Semi-quantitative RT-PCR and Western blot analysis revealed strong expression of Cx30 in thalamic nuclei. In line with coupling studies in Cx30ko mice these data indicate a minor role for Cx43 in gap junction coupling of astrocytes in the thalamus. Intriguingly, we found coupling between oligodendrocytes and astrocytes in the thalamus.These results indicate that thalamic glial cells differ in various aspects from their counterparts in other brain regions and support the emerging concept of glial heterogeneity.

Supported by DFG (SPP 1172, SFB-TR3) and EU (FP7-202167 Neuroglia).