Aims: The thalamus serves as an important relay for information reaching the cortex. Although neuronal circuitry are well investigated, yet little is known about properties and functions of glial cells in the thalamic nuclei. Recent studies have shown that astrocytes in the thalamus can modulate neuronal signalling upon intracellular Ca²⁺ increases travelling through the astrocytic network. In the present study we investigated basic morphological and functional properties of thalamic astrocytes. Methods: We combined electrophysiology and immunohistochemistry with semi quantitative RT-PCR to investigate receptor expression, gap junction coupling and antigen profiles. Investigation was focussed on the thalamic nuclei VPL and VPM, using transgenic mice with astrocyte-specific fluorescence labeling (GFAP-EGFP, Cx43-CFP ki). Astrocytes were analyzed between postnatal days 8 – 120. Results: Antibody staining demonstrated that only a subpopulation of thalamic astrocytes expressed GFAP while glutamine synthetase was found in almost all astrocytes. In freshly isolated, patch-clamped astrocytes, kainate induced small responses in a subset of the cells while much larger currents were evoked by GABA_A receptor activation. In GFAP-EGFP mice, biocytin filling during 20 min recording revealed profound gap junction coupling (n of coupled cells = 105 +/­ 31 cells). Unexpectedly, coupling was not decreased in Cx43-CFPki mice lacking one allele of Cx43. In Cx43-CFPki mice, SR101 filling of astrocytes and Two-Photon-microscopy identified a significant (41%) subset of SR101+ cells lacking CFP fluorescence. Together, these data indicate a minor role for Cx43 in gap junction coupling of astrocytes in the thalamus. Conclusions: These results indicate that thalamic astrocytes differ in various aspects from their counterpart in other brain regions and support the emerging concept of astrocyte heterogeneity. Supported by DFG (SFB TR3; SPP 1172 SE774/3) and EC (FP7-202167 Neuroglia).