| 19038445 |
Gilbert D, Lecchi M, Arnaudeau S, Bertrand D, Demaurex N: Local and global calcium signals associated with the opening of neuronal alpha7 nicotinic acetylcholine receptors. Cytotherapy. 2009;11(4):485-91.
Neuronal nicotinic acetylcholine receptors (nAChRs) are Ca (2+)-permeable ligand-gated channels widely expressed in the central and peripheral nervous system. One of the most Ca (2+) selective isoform is the homopentameric alpha7-nAChR implicated in schizophrenia. The activity of alpha7-nAChRs is usually recorded electrophysiologically, which limits the amount of information obtained. Here, we used fluorescence imaging to record Ca (2+) transients associated with activation of the alpha7-nAChR in neuroblastoma cells stably expressing human alpha7-nAChRs. Application of nicotine (50 microM) consistently evoked transient (30s), stereotyped Ca (2+) responses that were inhibited by the selective alpha7-nAChRs antagonists methyllycaconitine (MLA) and alpha-bungarotoxin, and greatly increased and prolonged by the allosteric modulator PNU-120596 (1 microM). Unexpectedly, brief (1-5s), repetitive Ca (2+) transients of sub-micrometric dimension were observed in filopodia of cells expressing alpha7-nAChR. PNU-120596 increased the frequency and slowed the decay kinetics of these miniature Ca (2+) elevations, which were insensitive to ryanodine, preserved during hyperpolarisation, and prevented by MLA, alpha-bungarotoxin, or Ca (2+) removal. Global Ca (2+) 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 Ca (2+) signals generated by alpha7-nAChRs can be recorded optically both in cell lines and in intact tissues. The possibility to image miniature Ca (2+) signals enables to map the location of functional alpha7-nAChR channel clusters within cells and to analyze their single channel properties optically. Deciphering the rich pattern of intracellular Ca (2+) signals generated by the activity of the alpha7-nAChRs will reveal the physiological role of these receptor-channels. |
2(0,0,0,2) |