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PLoS One. 2012;7(7):e39933. doi: 10.1371/journal.pone.0039933. Epub 2012 Jul 10.

An improved genetically encoded red fluorescent Ca2+ indicator for detecting optically evoked action potentials.

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1
Brain Science Institute, Saitama University, Saitama, Japan. mohkura@mail.saitama-u.ac.jp

Abstract

Genetically encoded Ca(2+) indicators (GECIs) are powerful tools to image activities of defined cell populations. Here, we developed an improved red fluorescent GECI, termed R-CaMP1.07, by mutagenizing R-GECO1. In HeLa cell assays, R-CaMP1.07 exhibited a 1.5-2-fold greater fluorescence response compared to R-GECO1. In hippocampal pyramidal neurons, R-CaMP1.07 detected Ca(2+) transients triggered by single action potentials (APs) with a probability of 95% and a signal-to-noise ratio >7 at a frame rate of 50 Hz. The amplitudes of Ca(2+) transients linearly correlated with the number of APs. The expression of R-CaMP1.07 did not significantly alter the electrophysiological properties or synaptic activity patterns. The co-expression of R-CaMP1.07 and channelrhodpsin-2 (ChR2), a photosensitive cation channel, in pyramidal neurons demonstrated that R-CaMP1.07 was applicable for the monitoring of Ca(2+) transients in response to optically evoked APs, because the excitation light for R-CaMP1.07 hardly activated ChR2. These technical advancements provide a novel strategy for monitoring and manipulating neuronal activity with single cell resolution.

PMID:
22808076
PMCID:
PMC3393713
DOI:
10.1371/journal.pone.0039933
[Indexed for MEDLINE]
Free PMC Article
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