Optogenetic Activation of Astrocytes—Effects on Neuronal Network Function

Abstract

Optogenetics approach is used widely in neurobiology as it allows control of cellular activity with high spatial and temporal resolution. In most studies, optogenetics is used to control neuronal activity. In the present study optogenetics was used to stimulate astrocytes with the aim to modulate neuronal activity. To achieve this goal, light stimulation was applied to astrocytes expressing a version of ChR2 (ionotropic opsin) or Opto-α1AR (metabotropic opsin). Optimal optogenetic stimulation parameters were determined using patch-clamp recordings of hippocampal pyramidal neurons’ spontaneous activity in brain slices as a readout. It was determined that the greatest increase in the number of spontaneous synaptic currents was observed when astrocytes expressing ChR2(H134R) were activated by 5 s of continuous light. For the astrocytes expressing Opto-α1AR, the greatest response was observed in the pulse stimulation mode (T = 1 s, t = 100 ms). It was also observed that activation of the astrocytic Opto-a1AR but not ChR2 results in an increase of the fEPSP slope in hippocampal neurons. Based on these results, we concluded that Opto-a1AR expressed in hippocampal astrocytes provides an opportunity to modulate the long-term synaptic plasticity optogenetically, and may potentially be used to normalize the synaptic transmission and plasticity defects in a variety of neuropathological conditions, including models of Alzheimer’s disease and other neurodegenerative disorders.

A Neuropsin-based Optogenetic Tool for Precise Control of Gq signaling

“…We demonstrate the power of cOpn5 optogenetics by showing the striking physiological and behavioral effects in response to cOpn5-mediated optical activation of astrocytes and neurons in vivo . By contrast, recent ex vivo studies show that opto-a1AR- and Opn4-mediated optogenetic stimulations slightly increase the amplitudes of Ca 2+ signals and only mildly modulate the frequency of Ca 2+ transients and synaptic events even after prolonged illumination 28, 29 . By overcoming the limitations of light sensitivity, temporal resolution, and response amplitudes associated with opto-a1AR- and Opn4-mediated optogenetics, cOpn5 should find broad applicability for studying G q signaling in numerous cells and tissues.…”

A neuropsin-based optogenetic tool for precise control of Gq signaling

“…We demonstrate the power of cOpn5 optogenetics by showing the striking physiological and behavioral effects in response to cOpn5mediated optical activation of neurons in vivo. By contrast, recent ex vivo studies show that opto-a1AR-and Opn4mediated optogenetic stimulations slightly increase the amplitudes of Ca 2+ signals and only mildly modulate the frequency of Ca 2+ transients and synaptic events even after prolonged illumination (Gerasimov et al, 2021;Mederos et al, 2019). By overcoming the limitations of light sensitivity, temporal resolution, and response amplitudes associated with opto-a1AR-and Opn4-mediated optogenetics, cOpn5 should find broad applicability for studying G q signaling in numerous cells and tissues.…”

“…However, cells expressing Opn4 isoforms show weak Ca 2+ responses even after prolonged (15-60 s) exposure to bright light illumination, and require continuous chromophore addition in the culture medium (Melyan et al, 2005;Mure et al, 2016;Qiu et al, 2005). Indeed, systematic characterizations have revealed major limitations of these two tools for in vitro and in vivo applications (Figueiredo et al, 2014;Gerasimov et al, 2021;Mederos et al, 2019). Opto-a1AR and Opn4 thus only partially mimic the activation of endogenous G q -coupled receptors.…”

Sex- and GABAergic-modulated neuronal subnetwork assemblies in the developing somatosensory cortex

“…One possible contribution to this could lie with astrocytes. Increasing astrocytes calcium dynamics induced long-lasting synaptic potentiation in the hippocampus (Gerasimov et al, 2021; Van Den Herrewegen et al, 2021). Astrocytes interact with neurons via their fine processes, which are developing from P7-P21 in S1 as well (Clavreul et al, 2019; Stogsdill et al, 2017).…”