Activity Dependent Modulation of Glial Gap Junction Coupling in the Thalamus

Paula Baum1, Camille Philippot1, Gerald Seifert1, Christian Steinhäuser1

1 Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Venusberg-Campus 1, 53127 Bonn, Germany

The thalamus plays an important role as a “gate to consciousness”, which is involved in controlling information transfer to the cortex. The ventral posterior nucleus (VPN), operating as a somato-sensory relay, contains elongated structures called barreloids, representing the somatotopic vibrissae organization. Astrocytes and oligodendrocytes in the VPN are coupled through gap junctions constituting panglial networks, restricted by barreloid borders formed by weakly coupled oligodendrocytes. Inhibition of neuronal activity decreases coupling efficiency in the thalamus. Therefore, we want to identify the connexin isoform regulated by neuronal activity and investigate whether neuronal activity regulates the efficiency of panglial coupling also in vivo. Cx30 is the dominant connexin isoform in thalamic astrocytes and was thought to be modulated by neuronal activity in olfactory glomeruli. To test whether Cx30 is sensitive to neuronal activity in the thalamus, experiments were performed in C57BL/6J and Cx30LacZ/LacZ mice. After pre-incubation of acute brain slices with ACSF or TTX and ω-conotoxin GVIA, an astrocyte within a barreloid was filled with biocytin and Texas Red Dextran through the patch pipette. Unexpectedly, in wildtype as well as in Cx30LacZ/LacZ mice the number of coupled cells was similarly decreased after inhibiting neuronal activity, arguing against Cx30 being sensitive to neuronal activity. Since our previous data revealed that Cx32 is the main connexin isoform expressed by oligodendrocytes in the thalamus, currently the effect of neuronal activity on coupling is investigated in Cx32-/- mice. In parallel, whisker trimming experiments have been started to investigate whether sensory deprivation affects panglial coupling in vivo.

Funded by EKFS and DFG (STE 552/4-3)