Intracellular Ca2+ signals evoked by stimulation of nicotinic acetylcholine receptors in SH‐SY5Y cells: contribution of voltage‐operated Ca2+ channels and Ca2+ stores

Journal of Neurochemistry - Tập 81 Số 3 - Trang 606-614 - 2002
Federico Dajas‐Bailador1, Adrian J. Mogg1, Susan Wonnacott1
1Department of Biology and Biochemistry, University of Bath, Bath, UK

Tóm tắt

AbstractNeuronal nicotinic acetylcholine receptors (nAChR) can regulate several neuronal processes through Ca2+‐dependent mechanisms. The versatility of nAChR‐mediated responses presumably reflects the spatial and temporal characteristics of local changes in intracellular Ca2+ arising from a variety of sources. The aim of this study was to analyse the components of nicotine‐evoked Ca2+ signals in SH‐SY5Y cells, by monitoring fluorescence changes in cells loaded with fluo‐3 AM. Nicotine (30 µm) generated a rapid elevation in cytoplasmic Ca2+ that was partially and additively inhibited (40%) by α7 and α3β2* nAChR subtype selective antagonists; α3β4* nAChR probably account for the remaining response (60%). A substantial blockade (80%) by CdCl2 (100 µm) indicates that voltage‐operated Ca2+ channels (VOCC) mediate most of the nicotine‐evoked response, although the α7 selective antagonist α‐bungarotoxin (40 nm) further decreased the CdCl2‐ resistant component. The elevation of intracellular Ca2+ levels provoked by nicotine was sustained for at least 10 min and required the persistent activation of nAChR throughout the response. Intracellular Ca2+ stores were implicated in both the initial and sustained nicotine‐evoked Ca2+ responses, by the blockade observed after ryanodine (30 µm) and the inositoltriphosphate (IP3)‐receptor antagonist, xestospongin‐c (10 µm). Thus, nAChR subtypes are differentially coupled to specific sources of Ca2+: activation of nAChR induces a sustained elevation of intracellular Ca2+ levels which is highly dependent on the activation of VOCC, and also involves Ca2+ release from ryanodine and IP3‐dependent intracellular stores. Moreover, the α7, but not α3β2* nAChR, are responsible for a fraction of the VOCC‐independent nicotine‐evoked Ca2+ increase that appears to be functionally coupled to ryanodine sensitive Ca2+ stores.

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Journal of Neurochemistry

Tập 81 Số 3

606-614

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