Imaging calcium signals in vivo: a powerful tool in physiology and pharmacology

Abstract

The design and engineering of organic fluorescent Ca 2+ indicators approximately 30 years ago opened the door for imaging cellular Ca 2+ signals with a high degree of temporal and spatial resolution. Over this time, Ca 2+ imaging has revolutionized our approaches for tissue-level spatiotemporal analysis of functional organization and has matured into a powerful tool for in situ imaging of cellular activity in the living animal. In vivo Ca 2+ imaging with temporal resolution at the millisecond range and spatial resolution at micrometer range has been achieved through novel designs of Ca 2+ sensors, development of modern microscopes and powerful imaging techniques such as two-photon microscopy. Imaging Ca 2+ signals in ensembles of cells within tissue in 3D allows for analysis of integrated cellular function, which, in the case of the brain, enables recording activity patterns in local circuits. The recent development of miniaturized compact, fibre-optic-based, mechanically flexible microendoscopes capable of two-photon microscopy opens the door for imaging activity in awake, behaving animals. This development is poised to open a new chapter in physiological experiments and for pharmacological approaches in the development of novel therapies. LINKED ARTICLESThis article is part of a themed section on Imaging. To view the other articles in this section visit http://dx.doi.org/10.1111/ bph.2011.163.issue-8 BJP has previously published an Imaging in Pharmacology themed section, edited by A Davenport and C Daly. To view this section visit http://dx

In vitro and in vivo imaging of intracellular Ca2+ responses in salivary gland cells

“…Intravital imaging enables the study of the association between the intracellular dynamics of various signaling factors and the physiological function of target organs in live animals [14,37,38]. GECIs possess various advantages over organic fluorescent Ca 2 þ indicators; in particular, GECIs are not liable to suffer from leakage and are suitable for long-term experiments [39].…”

“…In particular, live cell Ca 2 þ imaging of salivary acinar cells revealed spatiotemporal changes in [Ca 2 þ ] i including Ca 2 þ waves and Ca 2 þ oscillations. Recent advances in imaging technologies, including fluorescent microscopy and the development of highly sensitive genetically encoded Ca 2 þ indicators (GECIs), have enabled the visualization of Ca 2 þ responses in live animals through intravital Ca 2 þ imaging in salivary acinar cells [14].…”

Astrocyte Calcium Signaling: From Observations to Functions and the Challenges Therein

“…Building on work with fluorescence resonance energy transfer based Ca 2þ indicators expressed in astrocytes (Atkin et al 2009;Russell 2011 indicators (GECIs) based on circularly permuted green fluorescent protein (Hires et al 2008;Tian et al 2009). We focused on using a membrane-targeted GECI and a cytosolic form (Fig.…”

In vivofiber photometry of neural activity in response to optogenetically manipulated inputs in freely moving mice

“…1,2 Fiber photometry detects the°uorescence change of Ca 2þ concentration monitored by indicators such as BAPTA-AM, Fura2-AM, Fluo3-AM, Fluo4-AM, or genetically encoded calcium indicators (GECIs), etc. 3,4 The increase of Ca 2þ concentration was generally used as a reporter of enhanced neuron activity due to Ca 2þ in°ux into activated neuron. 5,6 GCaMP protein is an extensively used GECI based on circularly permuted green°uorescent protein (cpGFP), calmodulin, 7 and the Ca 2þ /CaM-binding peptide (M13pep).…”