title: Astrocytes display complex and localized calcium responses to single-neuron stimulation in the hippocampus.
abstract: Astrocytes show a complex structural and physiological interplay with neurons and respond to neuronal activation in vitro and in vivo with intracellular calcium elevations. These calcium changes enable astrocytes to modulate synaptic transmission and plasticity through various mechanisms. However, the response pattern of astrocytes to single neuronal depolarization events still remains unresolved. This information is critical for fully understanding the coordinated network of neuron-glial signaling in the brain. To address this, we developed a system to map astrocyte calcium responses along apical dendrites of CA1 pyramidal neurons in hippocampal slices using single-neuron stimulation with channelrhodopsin-2. This technique allowed selective neuronal depolarization without invasive manipulations known to alter calcium levels in astrocytes. Light-evoked neuronal depolarization was elicited and calcium events in surrounding astrocytes were monitored using the calcium-sensitive dye Calcium Orange. Stimulation of single neurons caused calcium responses in populations of astrocytes along the apical axis of CA1 cell dendrites. Calcium responses included single events that were synchronized with neuronal stimulation and poststimulus changes in calcium event frequency, both of which were modulated by glutamatergic and purinergic signaling. Individual astrocytes near CA1 cells showed low ability to respond to repeated neuronal depolarization events. However, the response of the surrounding astrocyte population was remarkably accurate. Interestingly, the reliability of responses was graded with respect to astrocyte location along the CA1 cell dendrite, with astrocytes residing in the primary dendrite subregion being most responsive. This study provides a new perspective on the dynamic response property of astrocyte ensembles to neuronal activity.
authors.affiliation: Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada, H3G 1A4.
authors.forename: Yann
authors.initials: Y
authors.lastname: Bernardinelli
authors.forename: Chris
authors.initials: C
authors.lastname: Salmon
authors.forename: Emma V
authors.initials: EV
authors.lastname: Jones
authors.forename: W Todd
authors.initials: WT
authors.lastname: Farmer
authors.forename: David
authors.initials: D
authors.lastname: Stellwagen
authors.forename: Keith K
authors.initials: KK
authors.lastname: Murai
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D001253:Astrocytes / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics; D001565:Benzoates / Q000494:pharmacology; D048588:Benzoxazines / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002229:Carbenoxolone / Q000494:pharmacology; D000075402:Channelrhodopsins; D004558:Electric Stimulation / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus / Q000166:cytology*; D066298:In Vitro Techniques; D008164:Luminescent Proteins / Q000235:genetics; D008297:Male; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D009474:Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010446:Peptide Fragments / Q000494:pharmacology; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D010775:Photic Stimulation / Q000379:methods; D010880:Piperidines / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D026941:Sodium Channel Blockers / Q000494:pharmacology; D018709:Statistics, Nonparametric; D013744:Tetanus Toxin / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014161:Transduction, Genetic / Q000379:methods
chemical_list: C508240:(2S,3S)-3-(3-(4-(trifluoromethyl)benzoylamino)benzyloxy)aspartate; D001426:Bacterial Proteins; D001565:Benzoates; D048588:Benzoxazines; D002121:Calcium Channel Blockers; D000075402:Channelrhodopsins; D018691:Excitatory Amino Acid Antagonists; D005904:Glial Fibrillary Acidic Protein; D008164:Luminescent Proteins; D009025:Morpholines; D009281:Naphthalenes; D010446:Peptide Fragments; D010880:Piperidines; D011720:Pyrazoles; D011725:Pyridines; D026941:Sodium Channel Blockers; D013744:Tetanus Toxin; C485184:enhanced green fluorescent protein; C549316:tetanus toxin (947-966); C054562:yellow fluorescent protein, Bacteria; C079694:alpha-methyl-4-carboxyphenylglycine; D049452:Green Fluorescent Proteins; D001224:Aspartic Acid; C103505:AM 251; D013779:Tetrodotoxin; D008734:Methoxyhydroxyphenylglycol; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; C121465:6-methyl-2-(phenylethynyl)pyridine; D010751:Phosphopyruvate Hydratase; D002229:Carbenoxolone; D002118:Calcium; D005998:Glycine; C010117:3,4-dihydroxyphenylglycol