title: Imaging intracellular Ca²⁺ signals in striatal astrocytes from adult mice using genetically-encoded calcium indicators.
abstract: Astrocytes display spontaneous intracellular Ca(2+) concentration fluctuations ([Ca(2+)]i) and in several settings respond to neuronal excitation with enhanced [Ca(2+)]i signals. It has been proposed that astrocytes in turn regulate neurons and blood vessels through calcium-dependent mechanisms, such as the release of signaling molecules. However, [Ca(2+)]i imaging in entire astrocytes has only recently become feasible with genetically encoded calcium indicators (GECIs) such as the GCaMP series. The use of GECIs in astrocytes now provides opportunities to study astrocyte [Ca(2+)]i signals in detail within model microcircuits such as the striatum, which is the largest nucleus of the basal ganglia. In the present report, detailed surgical methods to express GECIs in astrocytes in vivo, and confocal imaging approaches to record [Ca(2+)]i signals in striatal astrocytes in situ, are described. We highlight precautions, necessary controls and tests to determine if GECI expression is selective for astrocytes and to evaluate signs of overt astrocyte reactivity. We also describe brain slice and imaging conditions in detail that permit reliable [Ca(2+)]i imaging in striatal astrocytes in situ. The use of these approaches revealed the entire territories of single striatal astrocytes and spontaneous [Ca(2+)]i signals within their somata, branches and branchlets. The further use and expansion of these approaches in the striatum will allow for the detailed study of astrocyte [Ca(2+)]i signals in the striatal microcircuitry.
authors.affiliation: Department of Physiology, University of California Los Angeles.
authors.forename: Ruotian
authors.initials: R
authors.lastname: Jiang
authors.affiliation: Department of Physiology, University of California Los Angeles.
authors.forename: Martin D
authors.initials: MD
authors.lastname: Haustein
authors.affiliation: Department of Neurobiology, University of California Los Angeles.
authors.forename: Michael V
authors.initials: MV
authors.lastname: Sofroniew
authors.affiliation: Department of Physiology, University of California Los Angeles; Department of Neurobiology, University of California Los Angeles; BKhakh@mednet.ucla.edu.
authors.forename: Baljit S
authors.initials: BS
authors.lastname: Khakh
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001253:Astrocytes / Q000737:chemistry* / Q000378:metabolism; D002118:Calcium / Q000032:analysis* / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D003342:Corpus Striatum / Q000737:chemistry* / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D044169:Receptors, Calcium-Sensing / Q000235:genetics / Q000378:metabolism
chemical_list: D044169:Receptors, Calcium-Sensing; D002118:Calcium