Blocking of Dendrodendritic Inhibition Unleashes Widely Spread Lateral Propagation of Odor-evoked Activity in the Mouse Olfactory Bulb. (1st November 2018)

• Record Type: Journal Article
• Authors: Shang, Mengjuan; Xing, Junling
• Is Part Of: Neuroscience. Volume 391(2018)
• Page Start: 50
• Page End: 59
• Publication Date: 2018-11-01
• Subjects: ACSF artificial cerebrospinal fluid -- APV D(−)-2-amino-5-phosphonopentanoic acid -- CNQX 6-cyano-7-nitroquinoxaline-2, 3-dione disodium salt -- dOB dorsal olfactory bulb -- EPL external plexiform layer -- GCaMP2 genetically encoded Ca2+ indicator protein -- GFP green fluorescence protein -- OB olfactory bulb -- ON olfactory nerve -- PBS phosphate buffered saline; olfactory bulb -- external plexiform layer -- mitral cell -- reciprocal synapses -- lateral inhibition -- calcium imaging; Neurochemistry -- Periodicals; Neurophysiology -- Periodicals; Neurology -- Periodicals; Neurochimie -- Périodiques; Neurophysiologie -- Périodiques; Neurochemistry; Neurophysiology; Electronic journals; Periodicals; Electronic journals; 612.8
• DOI: 10.1016/j.neuroscience.2018.09.003
• Languages: English
• ISSNs: 0306-4522

Abstract

Highlights: Physiological odorant processing in vivo at olfactory bulb level is open to debate. Olfactory bulb reveals specific optical imaging patterns of glomerular activation in GCaMP2 mouse. In vivo -activation of GABAergic receptors confine the signal transduction along mitral cell secondary dendrite. The mitral-granual-reciprocal synapses should work during odor-evoked response in physiological situation. Abstract: The olfactory circuitry in mice involves a well-characterized, vertical receptor type-specific organization, but the localized inhibitory effect from granule cells on action potentials that propagate laterally in secondary dendrites of mitral cell remains open to debate. To understand the functional dynamics of the lateral (horizontal) circuits, we analyzed odor-induced signaling using transgenic mice expressing a genetically encoded Ca 2+ indicator specifically in mitral/tufted and some juxtaglomerular cells. Optical imaging of the dorsal olfactory bulb (dOB) revealed specific patterns of glomerular activation in response to odor presentation or direct electric stimulation of the olfactory nerve (ON). Application of a mixture of ionotropic and metabotropic glutamate receptor antagonists onto the exposed dOB completely abolished the responses to direct stimulation of the ON as well as discrete odor-evoked glomerular responses patterns, while a spatially more widespread response component increased and expanded into previously nonresponsive regions. To test whether the widespread odor response component represented signal propagation along mitral cell secondary dendrites, an NMDA receptor antagonist alone was applied to the dOB and was found to also increase and expand odor-evoked response patterns. Finally, with dOB excitatory synaptic transmission completely blocked, application of 1 mM muscimol (a GABAA receptor agonist) to a circumscribed volume in the deep external plexiform layer (EPL) induced an odor non-responsive area. These results indicate that odor stimulation can activate olfactory reciprocal synapses and control lateral interactions among olfactory glomerular modules along a wide range of mitral cell secondary dendrites by modulating the inhibitory effect from granule cells.