کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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2166443 | 1091855 | 2009 | 10 صفحه PDF | دانلود رایگان |
Neuronal nicotinic acetylcholine receptors (nAChRs) are Ca2+-permeable ligand-gated channels widely expressed in the central and peripheral nervous system. One of the most Ca2+ selective isoform is the homopentameric α7-nAChR implicated in schizophrenia. The activity of α7-nAChRs is usually recorded electrophysiologically, which limits the amount of information obtained. Here, we used fluorescence imaging to record Ca2+ transients associated with activation of the α7-nAChR in neuroblastoma cells stably expressing human α7-nAChRs. Application of nicotine (50 μM) consistently evoked transient (30 s), stereotyped Ca2+ responses that were inhibited by the selective α7-nAChRs antagonists methyllycaconitine (MLA) and α-bungarotoxin, and greatly increased and prolonged by the allosteric modulator PNU-120596 (1 μM). Unexpectedly, brief (1–5 s), repetitive Ca2+ transients of sub-micrometric dimension were observed in filopodia of cells expressing α7-nAChR. PNU-120596 increased the frequency and slowed the decay kinetics of these miniature Ca2+ elevations, which were insensitive to ryanodine, preserved during hyperpolarisation, and prevented by MLA, α-bungarotoxin, or Ca2+ removal. Global Ca2+ responses were also recorded in ganglion cells of embryo chicken retina during co-application of PNU-120596 and nicotine, together with whole-cell currents and brief current bursts. These data demonstrate that Ca2+ signals generated by α7-nAChRs can be recorded optically both in cell lines and in intact tissues. The possibility to image miniature Ca2+ signals enables to map the location of functional α7-nAChR channel clusters within cells and to analyze their single channel properties optically. Deciphering the rich pattern of intracellular Ca2+ signals generated by the activity of the α7-nAChRs will reveal the physiological role of these receptor-channels.
Journal: Cell Calcium - Volume 45, Issue 2, February 2009, Pages 198–207