Charakterisierung von Calcium-Transienten in Astrozyten der ventralen respiratorischen Gruppe

Abstract

Astrocytes are described as one of the major cell population in the brain of mammals and show a special form of excitability, which is based on changes of intracellular Ca2+-concentrations. Astrocytes actively participate in the integration and modulation of synaptic processes in the brain. The aim of this study was to characterize Ca2+-signals in astrocytes of the respiratory center and to elucidate their function within this neuronal network.In the present study it could be shown, that the inward rectifying potassium channel Kir4.1 is the molecular substrate for an astrocyte specific Ca2+-signal, which is induced by lowering the extracellular potassium. Using different transgenic mouse lines with different fluorescently labelled cell populations, this Ca2+-signal could be observed in situ only in astrocytes, but not in neurons and oligodendrocytes.Furthermore the functional expression of metobotropic receptors in astrocytes of the respiratory center could be detected. For the first time this provides evidence, that neuromodulators of the respiratory system such as serotonin, thyreotropin releasing hormone and substance P can directly affect astrocytes. Via intracellular Ca2+-elevations mediated by 5-HT2a-, NK1- and TRH-receptors, astrocytes could possibly react to neuromodulator release from neurons modulating the respiratory network. Such calcium rise might then indirectly influence neighbouring respiratory neurons.