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Variable action potential backpropagation during tonic firing and low-threshold spike bursts in thalamocortical but not thalamic reticular nucleus neurons


Connelly, WM and Crunelli, V and Errington, AC, Variable action potential backpropagation during tonic firing and low-threshold spike bursts in thalamocortical but not thalamic reticular nucleus neurons, Journal of Neuroscience, 37, (21) pp. 5319-5333. ISSN 0270-6474 (2017) [Refereed Article]


Copyright Statement

Copyright 2017 Connelly et al. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0)

DOI: doi:10.1523/JNEUROSCI.0015-17.2017


Backpropagating action potentials (bAPs) are indispensable in dendritic signaling. Conflicting Ca 2-imaging data and an absence of dendritic recording data meansthatthe extent of backpropagation inthalamocortical (TC) andthalamic reticular nucleus (TRN) neurons remains unknown. Because TRN neurons signal electrically through dendrodendritic gap junctions and possibly via chemical dendritic GABAergic synapses, as well as classical axonal GABA release, this lack of knowledge is problematic. To address this issue, we made two-photon targeted patch-clamp recordings from rat TC and TRN neuron dendrites to measure bAPs directly. These recordings reveal that "tonic" and low-threshold-spike (LTS) "burst" APs in both cell types are always recorded first at the soma before backpropagating into the dendrites while undergoing substantial distance-dependent dendritic amplitude attenuation. In TC neurons, bAP attenuation strength varies according to firing mode. During LTS bursts, somatic AP half-width increases progressively with increasing spike number, allowing late-burst spikes to propagate more efficiently into the dendritic tree compared with spikes occurring at burst onset. Tonic spikes have similar somatic half-widths to late burst spikes and undergo similar dendritic attenuation. In contrast, in TRN neurons, AP properties are unchanged between LTS bursts and tonic firing and, as a result, distance-dependent dendritic attenuation remains consistent across different firing modes. Therefore, unlike LTS-associated global electrical and calcium signals, the spatial influence of bAP signaling in TC and TRN neurons is more restricted, with potentially important behavioral-state-dependent consequences for synaptic integration and plasticity in thalamic neurons.

Item Details

Item Type:Refereed Article
Keywords:Vision, thalamus, synaptic integration, non-linear systems
Research Division:Biomedical and Clinical Sciences
Research Group:Neurosciences
Research Field:Cellular nervous system
Objective Division:Health
Objective Group:Clinical health
Objective Field:Clinical health not elsewhere classified
UTAS Author:Connelly, WM (Dr William Connelly)
ID Code:131554
Year Published:2017
Web of Science® Times Cited:5
Deposited By:Medicine
Deposited On:2019-03-22
Last Modified:2022-08-23
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