title: Using Intrinsic Flavoprotein and NAD(P)H Imaging to Map Functional Circuitry in the Main Olfactory Bulb.
abstract: Neurons exhibit strong coupling of electrochemical and metabolic activity. Increases in intrinsic fluorescence from either oxidized flavoproteins or reduced nicotinamide adenine dinucleotide (phosphate) [NAD(P)H] in the mitochondria have been used as an indicator of neuronal activity for the functional mapping of neural circuits. However, this technique has not been used to investigate the flow of olfactory information within the circuitry of the main olfactory bulb (MOB). We found that intrinsic flavoprotein fluorescence signals induced by electrical stimulation of single glomeruli displayed biphasic responses within both the glomerular (GL) and external plexiform layers (EPL) of the MOB. Pharmacological blockers of mitochondrial activity, voltage-gated Na+ channels, or ionotropic glutamate receptors abolished stimulus-dependent flavoprotein responses. Blockade of GABAA receptors enhanced the amplitude and spatiotemporal spread of the flavoprotein signals, indicating an important role for inhibitory neurotransmission in shaping the spread of neural activity in the MOB. Stimulus-dependent spread of fluorescence across the GL and EPL displayed a spatial distribution consistent with that of individual glomerular microcircuits mapped by neuroanatomic tract tracing. These findings demonstrated the feasibility of intrinsic fluorescence imaging in the olfactory systems and provided a new tool to examine the functional circuitry of the MOB.
authors.affiliation: Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.|Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Cedric R
authors.identifier: http://orcid.org/0000-0003-1625-3988
authors.initials: CR
authors.lastname: Uytingco
authors.affiliation: Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.|Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Puche
authors.affiliation: Center for Smell and Taste, University of Florida, Gainesville, Florida, United States of America.|Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida, United States of America.|Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Steven D
authors.initials: SD
authors.lastname: Munger
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D005260:Female; D005420:Flavoproteins / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D009249:NADP / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D009830:Olfactory Bulb / Q000166:cytology / Q000502:physiology*; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*
chemical_list: D005420:Flavoproteins; D009249:NADP