Imaging analysis of effect of anesthetics on intracellular calcium ion dynamics of dorsal root ganglia examined by a real-time confocal microscope

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Because adenosine trisphosphate (ATP) plays a pivotal role in causing inflammatory processes and pain, effects of ATP on dorsal root ganglion (DRG) has been extensively studied by electrophysiological methods. However, in the previous studies, satellite cells surrounding ganglion cells were ignored. We are skeptical about results based on isolated ganglion cells. The present study aimed to reveal the effects of ATP on ganglion and satellite cells, to this end we observed intracellular Ca^<2+> ion concentration ([Ca^<2+>]_i) change in DRG which kept structural integrities. DRG were taken out from immature (E20D) and mature (8W) rats. The [Ca^<2+>]_i changes during ATP stimulation were analysed by a confocal microscope. In immature and mature DRG, both ganglion and satellite cells responded to ATP. The ATP-induced [Ca^<2+>]_i increase of ganglion cells was rapid, and the decline was slow, while the satellite cell responses were spike-like. Only 1-3% of ganglion cells showed ATP-induced [Ca^<2+>]I changes, and about 40% of satellite cells responded. Based on the dependence of the response on presence of extracellular Ca^<2+> and the agonist, stimulations, ganglion and satellite cells possessed P2X and/or P2Y. There were no significant differences on ganglion cell responses between immature and mature DRG. In immature satellite cells, the response was single-shot, while mature satellite cells showed oscillatory fluctuation. Present results indicate that population of ganglion cells responding to ATP was low. Previous studies might confuse responses of satellite cells and those of ganglion cells. Oscillatory fluctuations appeared in mature satellite cells indicated a change of intracellular signaling mechanism during postnatal development. And this study showed that lidocaine inhibits the Ca^<2+> response of ganglion and satellite cells