DOI: 10.5061/dryad.h70rxwdmd
title: Astrocytic Gi-GPCR activation enhances stimulus-evoked extracellular glutamate

description: Astrocytes perform critical functions in the nervous system, many of which
 are dependent on neurotransmitter-sensing through G protein-coupled
 receptors (GPCRs). However, whether specific astrocytic outputs follow
 specific GPCR activity remains unclear, and exploring this question is
 critical for understanding how astrocytes ultimately influence brain
 function and behavior. Here, we investigate the outputs of astrocytic
 Gi-GPCRs, a family of GPCRs which we previously showed is sufficient to
 increase slow-wave neural activity (SWA) during sleep when activated in
 cortical astrocytes1. We focus on two putative outputs by astrocytes in
 vivo, the regulation of extracellular glutamate and GABA, by combining
 fiber photometry recordings of the extracellular indicators iGluSnFR and
 iGABASnFR with astrocyte-specific chemogenetic Gi-GPCR activation. We find
 that Gi-GPCR activation does not change spontaneous dynamics of
 extracellular glutamate or GABA. However, Gi-GPCR activation does
 specifically increase visual stimulus-evoked extracellular glutamate.
 Together, these data point towards a complex relationship between
 astrocytic inputs and outputs in vivo that may depend on behavioral
 context. Further, they suggest an extracellular glutamate-specific
 mechanism underlying some astrocytic Gi-GPCR-dependent behaviors,
 including the regulation of sleep SWA.
description: All procedures were carried out in adult mice (C57Bl/6, P50–100,
 males and females). Mice underwent surgery to implant fiber optic cannulas
 as well as viral injections of relevant viruses including
 AAV-GFAP.SF-iGluSnFR.AI184S, AAV-GFAP-iGABASnFR2, AAV-GFAP-GCaMP6f, and
 AAV5-GFAP-hM4D(Gi)-mCherry in V1. Mice were first habituated to the
 recording setup. On the day of recording, mice were tethered to the
 recording setup via a patchcord and then injected I.P. with CNO (1 mg/kg)
 or saline (0.9%) immediately prior to recording. Four recordings were made
 in the following order: spontaneous (no LED, 10-min), LED flash stimuli
 (10-min), spontaneous (no LED, 30-min), LED flash stimuli (10-min) for a
 total of 1-hour. We used a Tucker-Davis Technologies RZ10X Processor with
 a Doric Lenses fluorescence mini-cube. A 473nm LED was used for the
 iGluSnFR and iGABASnFR2 excitation and a 405nm LED was used as an
 isobestic control. Both LEDs (Tucker-Davis Technologies, RZ10X Processor)
 went through a fluorescence mini-cube (Doric Lenses), and then through
 patchcords connected to a commutator to allow for free movement of the
 animal. After the commutator, a patchcord was connected to the fiber-optic
 cannula implanted in the animal. Fluorescence signals were reflected back
 through the mini-cube to a photoreceiver on the RZ10X Processor. The
 dataset provided contains the raw data that is outputted by the Synapse
 recording software.
description: This dataset is split into two parts: SnFR data (GluSnFR and
 GABASnFR photometry data) and GCaMP data. Each part is saved as a MAT file
 containing a single matlab structure array. For SnFR data, the strucutre
 array contains N rows where each row corresponds to an individual
 photometry recording. For GCaMP data, the structure array contains N rows
 where each row corresponds to a mouse and contains individual photometry
 recordings for that mouse as separate fields within the row. Each
 structure array contains many different fields that include metadata for
 the animal, recording information, as well as the raw data. A description
 of each field is found in the ReadMe file that is attached. In the code
 provided, the code relies on using the raw data in the structure array as
 well as saving new fields into the structure for processed data of various
 stages. All data for all animals and recordings are included. In any
 instance where duplicate data exists or animals are excluded, it is
 referenced in the code.