Piet Richard, Jahr Craig E
Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239, USA.
J Neurosci. 2007 Apr 11;27(15):4027-35. doi: 10.1523/JNEUROSCI.0462-07.2007.
Astrocytes respond to neuronal activity with [Ca2+]i increases after activation of specific receptors. Bergmann glial cells (BGs), astrocytes of the cerebellar molecular layer (ML), express various receptors that can mobilize internal Ca2+. BGs also express Ca2+ permeable AMPA receptors that may be important for maintaining the extensive coverage of Purkinje cell (PC) excitatory synapses by BG processes. Here, we examined Ca2+ signals in single BGs evoked by synaptic activity in cerebellar slices. Short bursts of high-frequency stimulation of the ML elicited Ca2+ transients composed of a small-amplitude fast rising phase, followed by a larger and slower rising phase. The first phase resulted from Ca2+ influx through AMPA receptors, whereas the second phase required release of Ca2+ from internal stores initiated by P2 purinergic receptor activation. We found that such Ca2+ responses could be evoked by direct activation of neurons releasing ATP onto BGs or after activation of metabotropic glutamate receptor 1 on these neurons. Moreover, examination of BG and PC responses to various synaptic stimulation protocols suggested that ML interneurons are likely the cellular source of ATP.
星形胶质细胞在特定受体激活后，通过细胞内钙离子浓度（[Ca2+]i）升高来响应神经元活动。伯格曼胶质细胞（BGs）是小脑分子层（ML）的星形胶质细胞，表达多种能够动员细胞内钙离子的受体。BGs还表达钙离子通透的AMPA受体，这对于BGs突起维持浦肯野细胞（PC）兴奋性突触的广泛覆盖可能很重要。在这里，我们研究了小脑切片中突触活动诱发的单个BGs中的钙离子信号。对ML进行高频刺激的短串刺激引发了钙离子瞬变，其由一个小幅度快速上升阶段和随后一个幅度更大、上升更慢的阶段组成。第一阶段是由钙离子通过AMPA受体流入引起的，而第二阶段则需要由P2嘌呤能受体激活引发的细胞内钙库释放钙离子。我们发现，这种钙离子反应可以通过直接激活向BGs释放ATP的神经元或激活这些神经元上的代谢型谷氨酸受体1后诱发。此外，对BGs和PCs对各种突触刺激方案的反应进行检查表明，ML中间神经元可能是ATP的细胞来源。
