Panglial calcium signalling in the olfactory bulb

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During the past two decade, it has become more and more obvious that glial cells are essential and active components of the nervous system contributing to brain function. Few studies have shown that different types of glial cells such as astrocytes and oligodendrocytes are coupled by gap junctions to each other to form so-called panglial networks. Panglial networks are supposed to support K+ siphoning and metabolic supply of axons, however, whether calcium signalling is transmitted from one type of glial cell to another via panglial routes has not been shown before. The proposed project aims to show that in mice calcium transients evoked in astrocytes can be transmitted to olfactory ensheathing glial cells (OECs), a specialized type of glial cells that share properties of both astrocytes and oligodendrocytes. OECs are found in the superficial layer of the olfactory bulb, the nerve layer, where they ensheath bundles of axons and are well seperated from astrocyte cell bodies which are located in deeper layers of the olfactory bulb. However, astrocytes project some proccesses into the nerve layer, suggesting possible interactions between astrocytes and OECs. Our preliminary results indicate that astrocytes and OECs are coupled by gap junctions formed by connexin 43. The proposed experiments will test the hypothesis that calcium transients locally evoked in astrocytes, e.g. by laser-mediated photoactivation of the "caged" agonist of metabotropic glutamate receptors, ACPD, can be transmitted to OECs via gap junctions and thereby establish panglial calcium signalling. Panglial calcium signalling subsequently triggers vasoresponses in blood vessels enwrapped by OECs. The project will contribute to our understanding how glial cells communicate with each other and how this accounts for regulation and maintenance of brain function.