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Detecting activity in olfactory bulb glomeruli with astrocyte recording
Didier De Saint Jan1, Gary L Westbrook
1Vollum Institute, Oregon Health and Sciences University, Portland, Oregon 97239, USA. desaintj@ohsu.edu
Summary
Olfactory bulb astrocytes detect neuronal activity, revealing compartmentalized synaptic transmission. This study highlights how astrocyte recordings can map complex signaling within olfactory glomeruli.
Area of Science:
- Neuroscience
- Olfactory System Biology
- Cellular Electrophysiology
Background:
- Olfactory sensory neuron (OSN) axons expressing the same olfactory receptor converge in specific olfactory bulb glomeruli.
- Intraglomerular synapses are spatially segregated into subcompartments by astrocyte processes.
- Glomerular astrocytes can serve as detectors of neuronal activity due to their localized processes.
Purpose of the Study:
- To investigate intraglomerular synaptic transmission and functional compartmentalization within the olfactory bulb.
- To utilize astrocyte recordings as a tool to monitor neuronal activity within olfactory glomeruli.
- To elucidate the roles of different receptors and glutamate release mechanisms in olfactory bulb signaling.
Main Methods:
- Recording of inward currents in glomerular astrocytes following olfactory nerve stimulation.
- Pharmacological manipulation using barium to block potassium currents and unmask transporter currents.
- Analysis of astrocyte current dependence on AMPA, NMDA, and metabotropic glutamate receptors.
- Characterization of synaptic glutamate transporter currents.
Main Results:
- Astrocyte inward currents, primarily barium-sensitive potassium currents, reflect mitral/tufted cell depolarization.
- The astrocyte potassium current depends on AMPA, NMDA, and a novel metabotropic glutamate receptor 1 component.
- Blockade of potassium currents revealed synaptic glutamate transporter currents influenced by both OSN and mitral/tufted cell dendrite glutamate release.
- Evidence suggests synchronous glutamate release at OSN terminals triggers asynchronous release from mitral/tufted cells.
Conclusions:
- Glomerular astrocyte recordings provide a sensitive method for studying functional compartmentalization within the olfactory bulb.
- Astrocyte activity is intricately linked to synaptic transmission involving multiple receptor types and distinct glutamate release sites.
- The findings reveal a novel mechanism of asynchronous glutamate release from mitral/tufted cells triggered by OSN input.