Astrocyte-to-neuron communication: functional relevance for synaptic transmission in the respiratory network?

星形胶质细胞现在已被确认为正常大脑功能的关键角色。据推测，最重要的是它们对神经元环境的稳定做出了贡献，因为它们有能力调节细胞外钾和神经递质的浓度。此外，星形胶质细胞本身可以利用和释放递质(即所谓的胶质递质)来向神经元发出信号。星形胶质细胞与神经元之间的这种联系依赖于星形胶质细胞释放钙离子，如谷氨酸或三磷酸腺苷，因此，星形胶质细胞能够直接影响突触传递。然而，在呼吸中枢，我们对星形胶质细胞衍生的递质分子在呼吸神经元之间突触中的作用的了解仍然很初级。在拟议的项目中，我们将回答以下关于延髓尾侧腹侧呼吸群(VRG)中星形胶质细胞与神经元通讯的问题：VRG中的星形胶质细胞是否向邻近的呼吸神经元和突触释放神经胶质递质？自发的星形胶质细胞钙振荡是否触发VRG星形胶质细胞释放神经胶质递质？需要哪些条件才能影响整个网络？为了回答这些问题，我们将结合电生理和光学技术。我们将对已识别的星形胶质细胞和邻近的呼吸神经元进行双重全细胞记录。这使得一方面可以通过电刺激、去笼子第二信使或特定拮抗剂的细胞内灌流来直接操纵星形胶质细胞，另一方面可以通过记录抑制性或兴奋性突触后电流来监测突触传递。同时，我们将在持续的呼吸网络活动中对星形胶质细胞钙信号进行成像和调制。

Astrocytes have now been identified as key players for normal brain function. Presumably most important is their contribution to the stabilization of the environment of neurons, due to their capability to regulate the extracellular concentration of potassium as well as neurotransmitters. Moreover, it has become evident that astrocytes themselves can utilize and release transmitter (so called gliotransmitters) to signal to neurons. This kind of astrocyte-to-neuron communication has been shown to depend on a calcium-dependent release of e.g. glutamate or ATP from astrocytes, thus, astrocyte are capable to influence synaptic transmission directly. In the respiratory centre, however our understanding of the role of astrocyte-derived transmitter molecules for synapses between respiratory neurons is still rudimentary. In the proposed project we shall answer the following questions regarding astrocyte-to-neuron communication in the ventral respiratory group (VRG) of the caudal medulla: Do astrocytes in the VRG release gliotransmitters to neighboring respiratory neurons and synapses? Do spontaneous astrocytic calcium oscillations trigger gliotransmitter release in VRG astrocytes? Which conditions are required to influence the entire network? To answer these questions we will combine electrophysiological and optical techniques. We will perform dual whole-cell recordings from pairs of identified astrocytes and neighboring respiratory neurons. This allows on the one side a direct manipulation of the astrocyte using electrical stimulation, un-caging of second messengers or intracellular perfusion of specific antagonists and on the other to monitor synaptic transmission by recording inhibitory or excitatory postsynaptic currents. In parallel we will image and modulate astrocytic calcium signals during ongoing respiratory network activity.