Optogenetic Sensors for Monitoring Intracellular Chloride

Berglund, Ken; Lei, Wen; Augustine, George J

doi:10.1007/978-4-431-55516-2_11

Cited by 1 publication

(1 citation statement)

References 128 publications

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“…Moreover, we observed a delayed and slow fall in pH i , which is in agreement with analogous data obtained in dynamic measurements of brain tissue pH in vitro (26,43). It is worth noting that the time constant of Cl − interaction with LSSmClopHensor is identical to that of ClopHensor (29) and similar to that of Clomeleon and SuperClomeleon (53). This implies that the sensor signal is not likely to fully reflect the fast changes in [Cl − ] i that are bound to take place during seizures, but as is the case with genetically encoded sensors for calciumand ion-sensitive K + microelectrodes, ionic dynamics measured at rates corresponding to the present do provide useful information on the direction, magnitude, and time course of the net activity-induced Cl − flux.…”

Section: Discussion Properties and Advantages Of Lssmclophensor In Nesupporting

confidence: 89%

Simultaneous two-photon imaging of intracellular chloride concentration and pH in mouse pyramidal neurons in vivo

Sato

Artoni

Landi

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

132

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Intracellular chloride ([Cl−] i ) and pH (pH i ) are fundamental regulators of neuronal excitability. They exert wide-ranging effects on synaptic signaling and plasticity and on development and disorders of the brain. The ideal technique to elucidate the underlying ionic mechanisms is quantitative and combined two-photon imaging of [Cl − ] i and pH i , but this has never been performed at the cellular level in vivo. Here, by using a genetically encoded fluorescent sensor that includes a spectroscopic reference (an element insensitive to Cl − and pH), we show that ratiometric imaging is strongly affected by the optical properties of the brain. We have designed a method that fully corrects for this source of error. Parallel measurements of [Cl − ] i and pH i at the single-cell level in the mouse cortex showed the in vivo presence of the widely discussed developmental fall in [Cl − ] i and the role of the K-Cl cotransporter KCC2 in this process. Then, we introduce a dynamic twophoton excitation protocol to simultaneously determine the changes of pH i and [Cl − ] i in response to hypercapnia and seizure activity.I ntracellular ion concentrations are controlled by plasmalemmal transporters and channels, which generate and dissipate ionic electrochemical gradients, respectively (1). In recent years, regulation of the intracellular Cl − concentration ([Cl − ] i ) in neurons has attracted lots of attention, because it is the main ion that carries current across GABA A (and also, glycine) receptors. Changes in [Cl − ] i exert an immediate effect on the reversal potential of GABAergic currents (E GABA ) and, thereby, on the properties of GABA A receptor-mediated transmission (2-4). The "ionic plasticity" of GABAergic signaling involves not only the passive flux of Cl − ions through membrane channels but also, a number of ion transporters that regulate [Cl − ] i . Furthermore, this mechanism is under the control of intracellular signaling cascades that regulate the expression patterns as well as functional properties of ion transporters and channels (5, 6). With regard to long-term ionic modulation of GABAergic transmission, a case in point is the decrease in [Cl − ] i that is generally thought to take place during maturation of most central neurons. According to this widely accepted scenario, the Na-K-2Cl cotransporter NKCC1 accumulates Cl − in immature neurons, thereby promoting depolarizing GABA responses (3, 7-9), which is followed by developmental upregulation of the neuron-specific K-Cl cotransporter KCC2 that is required for the generation of classical hyperpolarizing inhibitory postsynaptic potentials (IPSPs) (10).A wealth of electrophysiological evidence dating back to the work in vivo by Eccles and coworkers (11) has provided evidence for active regulation of [Cl − ] i in mammalian central neurons and its crucial effect on the driving force of Cl − in inhibitory synapses (1). However, thus far, there are no direct data on neuronal [Cl − ] i measured in vivo at the single-cell level in the living brain, and for in...

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