title: Calcium imaging of odor-evoked responses in the Drosophila antennal lobe.
abstract: The antennal lobe is the primary olfactory center in the insect brain and represents the anatomical and functional equivalent of the vertebrate olfactory bulb. Olfactory information in the external world is transmitted to the antennal lobe by olfactory sensory neurons (OSNs), which segregate to distinct regions of neuropil called glomeruli according to the specific olfactory receptor they express. Here, OSN axons synapse with both local interneurons (LNs), whose processes can innervate many different glomeruli, and projection neurons (PNs), which convey olfactory information to higher olfactory brain regions. Optical imaging of the activity of OSNs, LNs and PNs in the antennal lobe - traditionally using synthetic calcium indicators (e.g. calcium green, FURA-2) or voltage-sensitive dyes (e.g. RH414) - has long been an important technique to understand how olfactory stimuli are represented as spatial and temporal patterns of glomerular activity in many species of insects. Development of genetically-encoded neural activity reporters, such as the fluorescent calcium indicators G-CaMP and Cameleon, the bioluminescent calcium indicator GFP-aequorin, or a reporter of synaptic transmission, synapto-pHluorin has made the olfactory system of the fruitfly, Drosophila melanogaster, particularly accessible to neurophysiological imaging, complementing its comprehensively-described molecular, electrophysiological and neuroanatomical properties. These reporters can be selectively expressed via binary transcriptional control systems (e.g. GAL4/UAS, LexA/LexAop, Q system) in defined populations of neurons within the olfactory circuitry to dissect with high spatial and temporal resolution how odor-evoked neural activity is represented, modulated and transformed. Here we describe the preparation and analysis methods to measure odor-evoked responses in the Drosophila antennal lobe using G-CaMP. The animal preparation is minimally invasive and can be adapted to imaging using wide-field fluorescence, confocal and two-photon microscopes.
authors.affiliation: Center for Integrative Genomics, University of Lausanne.
authors.forename: Ana F
authors.initials: AF
authors.lastname: Silbering
authors.forename: Rati
authors.initials: R
authors.lastname: Bell
authors.forename: C Giovanni
authors.initials: CG
authors.lastname: Galizia
authors.forename: Richard
authors.initials: R
authors.lastname: Benton
mesh_terms: D000818:Animals; D057506:Arthropod Antennae / Q000502:physiology; D002118:Calcium / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D004331:Drosophila melanogaster / Q000502:physiology*; D005456:Fluorescent Dyes / Q000737:chemistry*; D049452:Green Fluorescent Proteins / Q000737:chemistry; D008856:Microscopy, Fluorescence / Q000379:methods; D009812:Odorants; D012903:Smell / Q000502:physiology
chemical_list: D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins; D002118:Calcium