Morphine, Nmda Glutamate And Glial Cells Of Cultured Rat Stars The Influence Of The Calcium Oscillation

Glial cells are the most widely distributed cells in central nervous system (CNS). The classical view of glial cells as simple supportive cells for neurons is being replaced by a new vision that glial cells are active elements involved in the physiology of the nervous system. They are involved in the synaptic formation, the secretion and uptake of neurotransmitters, therefore modifying brain function. Glial cells are important to the regulation of neuronal information transfer in brain function under normal and pathological conditions, such as drug addiction, etc. Astrocyte, a subtype of glial cells in the CNS, has also been paid more and more attention. Unlike neurons that can generate action petentials, glial cells perform excitability via rising intracellular free Ca2+concentration ([Ca2+]i). While excited, astrocytes can release gliotransmitters that regulate synaptic efficacy and plasticity. Thus, the calcium signal of astrocyte become a hot topic in recent years.In this erperiment, the effects of glutamate, NMDA and morphine perfusion on [Ca2+]i of cultured astrocytes from rat cerebral cortex using Fura-2/AM loading method were tested to illuminate the possible receptor pathways of interaction between neurons and astrocytes, and the direct effects of opioid application on astrocytes.Astrocytes were separated from cerebral cortex of new born Sprague-Dawley (SD) rats (1-3days old). The cultured astrocytes were identified by immunocytochemistry that showed glial fibrilary acidic protein-positive (GFAP). We used Fura-2/AM as Ca2+indicator to detect changes of [Ca2+]i pre-and post-perfusion of glutamate, NMDA, morphine in astrocytes, respectively. We also examined the effects of blockage mGluR5, NMDA receptor(NMDAR)subunits, μ-Opioid receptor on induced intracellular calcium oscillations.It was showed that stimulated by glutamate, NMDA or morphine perfusion,[Ca2+]iof astrocytes was increased obviously, whereas this effect was bolished by the corresponding receptor antagonists, respectively.The results were as follows:1. L-glutamate could elevate [Ca2+]i in astrocyte.2. L-glutamate elevated astrocyte [Ca2+]i through the activation of mGluR5and NMDAR 3. Morphine induced astrocyte [Ca+]i elevation through the activation of μ-Opioid receptor.Conclusion:These results shows that mGluR5, NMDAR and μ-Opioid receptor exist on membrane of cultured rat astrocytes, and activation of these receptors can increase astrocytes [Ca2+]i. The modulation pathways of [Ca2+]i via these receptors might play an important role in the communication between astrocyes and neurons.