Imaging Calcium in Neurons

Abstract

Calcium ions generate versatile intracellular signals that control key functions in all types of neurons. Imaging calcium in neurons is particularly important because calcium signals exert their highly specific functions in well-defined cellular subcompartments. In this Primer, we briefly review the general mechanisms of neuronal calcium signaling. We then introduce the calcium imaging devices, including confocal and two-photon microscopy as well as miniaturized devices that are used in freely moving animals. We provide an overview of the classical chemical fluorescent calcium indicators and of the protein-based genetically encoded calcium indicators. Using application examples, we introduce new developments in the field, such as calcium imaging in awake, behaving animals and the use of calcium imaging for mapping single spine sensory inputs in cortical neurons in vivo. We conclude by providing an outlook on the prospects of calcium imaging for the analysis of neuronal signaling and plasticity in various animal models.

Long-term In Vivo Calcium Imaging of Astrocytes Reveals Distinct Cellular Compartment Responses to Sensory Stimulation

“…Process signals tended to occur in a particular region only in a single session. It is possible that different processes are activated at different times based on the local synaptic responses (Grienberger and Konnerth 2012). Our group has previously shown that a sparse population of neurons responds reliably over different time points to whisker stimulation (Margolis et al 2012;Mayrhofer et al 2015).…”

Direct interfacing of neurons to highly integrated microsystems

“…Extracellular electrical recordings by means of microtransducer arrays complement wellestablished patch clamp techniques [6,7] and optical or optogenetic techniques [8][9][10][11]. Commercially available standard MEAs (circuitless and passive) are an established technology for recording from networks of neurons [12][13][14][15].…”

“…Simultaneous recordings of multiple neurons are tedious to realize by patch-clamp, and the cells are only viable for a short time [19,20]. Optical and optogenetic methods provide multi-unit recording and stimulation over extended times, yet still have limited temporal resolution, and it is difficult to detect or to stimulate single action potentials (APs) in individual cells due to stray light and light scattering [3,[9][10][11].…”

Porphyrins for Probing Electrical Potential Across Lipid Bilayer Membranes by Second Harmonic Generation

“…However, changes in calcium concentration do not accurately reflect voltage transients. [4] Fluorescent voltage-sensitive dyes were first developed 30 years ago, [5] and recent advances in the molecular design of these dyes [6][7][8][9][10] have made it possible to track the spatial evolution of action potentials. [11][12][13][14] Compared with fluorescence, SHG imaging has several advantages as a technique for probing membrane potential: [3,[15][16][17][18][19][20][21] SHG has a greater intrinsic sensitivity to electric fields than fluorescence, [19][20][21] and it is only produced by noncentrosymmetric molecules in noncentrosymmetric environments, thus making it ideal for probing interfaces such as lipid bilayers.…”