title: Dynamics of intrinsic dendritic calcium signaling during tonic firing of thalamic reticular neurons.
abstract: The GABAergic neurons of the nucleus reticularis thalami that control the communication between thalamus and cortex are interconnected not only through axo-dendritic synapses but also through gap junctions and dendro-dendritic synapses. It is still unknown whether these dendritic communication processes may be triggered both by the tonic and the T-type Ca(2+) channel-dependent high frequency burst firing of action potentials displayed by nucleus reticularis neurons during wakefulness and sleep, respectively. Indeed, while it is known that activation of T-type Ca(2+) channels actively propagates throughout the dendritic tree, it is still unclear whether tonic action potential firing can also invade the dendritic arborization. Here, using two-photon microscopy, we demonstrated that dendritic Ca(2+) responses following somatically evoked action potentials that mimic wake-related tonic firing are detected throughout the dendritic arborization. Calcium influx temporally summates to produce dendritic Ca(2+) accumulations that are linearly related to the duration of the action potential trains. Increasing the firing frequency facilitates Ca(2+) influx in the proximal but not in the distal dendritic compartments suggesting that the dendritic arborization acts as a low-pass filter in respect to the back-propagating action potentials. In the more distal compartment of the dendritic tree, T-type Ca(2+) channels play a crucial role in the action potential triggered Ca(2+) influx suggesting that this Ca(2+) influx may be controlled by slight changes in the local dendritic membrane potential that determine the T-type channels' availability. We conclude that by mediating Ca(2+) dynamic in the whole dendritic arborization, both tonic and burst firing of the nucleus reticularis thalami neurons might control their dendro-dendritic and electrical communications.
authors.affiliation: UMR 7102 CNRS, Paris, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Chausson
authors.forename: Nathalie
authors.initials: N
authors.lastname: Leresche
authors.forename: Régis C
authors.initials: RC
authors.lastname: Lambert
mesh_terms: D000200:Action Potentials; D000818:Animals; D020013:Calcium Signaling; D003712:Dendrites / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013788:Thalamus / Q000166:cytology* / Q000378:metabolism / Q000502:physiology