Aghvami, S. Sara and Mueller, Max and Araabi, Babak N. and Egger, Veronica (2019) Coincidence Detection within the Excitable Rat Olfactory Bulb Granule Cell Spines. JOURNAL OF NEUROSCIENCE, 39 (4). pp. 584-595. ISSN 0270-6474,
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In the mammalian olfactory bulb, the inhibitory axonless granule cells (GCs) feature reciprocal synapses that interconnect them with the principal neurons of the bulb, mitral, and tufted cells. These synapses are located within large excitable spines that can generate local action potentials (APs) upon synaptic input ("spine spike"). Moreover, GCs can fire global APs that propagate throughout the dendrite. Strikingly, local postsynaptic Ca2+ entry summates mostly linearly with Ca2+ entry due to coincident global APs generated by glomerular stimulation, although some underlying conductances should be inactivated. We investigated this phenomenon by constructing a compartmental GC model to simulate the pairing of local and global signals as a function of their temporal separation Delta t. These simulations yield strongly sublinear summation of spine Ca2+ entry for the case of perfect coincidence Delta t = 0 ms. Summation efficiency (SE) sharply rises for both positive and negative Delta t. The SE reduction for coincident signals depends on the presence of voltage-gated Na+ channels in the spine head, while NMDARs are not essential. We experimentally validated the simulated SE in slices of juvenile rat brain (both sexes) by pairing two-photon uncaging of glutamate at spines and APs evoked by somatic current injection at various intervals Delta t while imaging spine Ca2+ signals. Finally, the latencies of synaptically evoked global APs and EPSPs were found to correspond to Delta t approximate to 10 ms, explaining the observed approximately linear summation of synaptic local and global signals. Our results provide additional evidence for the existence of the GC spine spike.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | BACKPROPAGATING ACTION-POTENTIALS; DENDRITIC SPINES; CALCIUM INFLUX; SYNAPTIC SIGNALS; NMDA RECEPTORS; NEURONS; SPIKE; INHIBITION; ACTIVATION; MECHANISMS; coincidence detection; granule cell; NEURON model; olfactory bulb; spine spike; two-photon uncaging |
| Subjects: | 500 Science > 570 Life sciences 500 Science > 590 Zoological sciences |
| Divisions: | Biology, Preclinical Medicine > Institut für Zoologie Biology, Preclinical Medicine > Institut für Zoologie > Neurophysiologie (Prof. Dr. Veronica Egger) |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 20 Apr 2020 09:31 |
| Last Modified: | 20 Apr 2020 09:31 |
| URI: | https://pred.uni-regensburg.de/id/eprint/27708 |
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