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@PHDTHESIS{Yang:749817,
author = {Yang, Danqing},
othercontributors = {Feldmeyer, Dirk and Kampa, Björn Michael},
title = {{C}haracterization of synaptic connections and cholinergic
modulation of layer 6{A} microcircuitry in rat barrel
cortex},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2018-230346},
pages = {1 Online-Ressource (109 Seiten) : Illustrationen,
Diagramme},
year = {2018},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University 2019; Dissertation, RWTH Aachen University, 2018},
abstract = {Of all neocortical layers, layer 6 is the least studied
layer that shows a relatively high neuronalheterogeneity and
low intralaminar connectivity. Layer 6A provides direct
projections from corticothalamic(CT) pyramidal cells to both
VPM and POM nucleus of the thalamus and are thus integral
part of a thalamo-cortical-thalamic feedback loop that
controls sensory signalling. In this study, we investigated
anatomical and functional properties of L6A intra-laminar
excitatory and inhibitory connections in L6A of rat barrel
cortex by performing dual whole-cell recordings with
simultaneousbiocytin fillings. The neuronal morphology was
subsequently reconstructed and putative CT
andcortico-cortical (CC) pyramidal cells were distinguished
based on their distinct axonal projection patterns. An
unsupervised cluster analysis were performed to classify FS
and nFS interneurons based on their electrophysiological
properties such as membrane properties and firing
properties. Thus, different types of connections were
identified based on pre- and postsynaptic neuronalsubtypes.
The intralaminar connectivity of L6A neurons is low with a
connectivity ratio of $6.5\%$ (n=79).There is a much higher
probability of a CC-like rather than a CT-like pyramidal
cell being presynaptic as well as postsynaptic. In response
to presynaptic APs elicited in CT-like pyramidal cells,
EPSPs showed remarkably smaller amplitude, larger PPR, CV
and failure rate recorded than those elicited by presynaptic
APs in CC L6A pyramidal cells. For excitatory-inhibitory
connections between CC cells and interneurons, FS and non-FS
interneuron exhibited short-term depression and
facilitation, respectively; while for connections between CT
cells and interneurons, facilitated EPSPs were observed
regardless of interneuron type. Moreover, we found that FS
interneurons trigger a ‘fast’ postsynaptic response with
short rise time and latency in excitatory neurons, whereas
nFS interneurons display ‘slow’ kinetics by generating
IPSPs with significantly longer rise time and latency.
Notably, reciprocal connections were found only between two
CC-like pyramidal cells orCC-interneurons, but not for
connections involving a CT pyramidal cell. Acetylcholine
(ACh) is released from the basal forebrain during different
behavioural states, e.g. wakefulness and attention and
differentially modulates neocortical neurons via both
nicotinic and muscarinic ACh receptors. Here we investigated
the cholinergic modulation of CT and CCpyramidal cells in
layer 6A of the barrel cortex. We found that ACh
differentially modulates theL6A microcircuitry by
persistently depolarizing CT but hyperpolarizing CC L6A
pyramidal cells, effects that are concentration-dependent
and are mediated via M1 and M4 mAChRs, respectively. ACh
application increases frequency of miniature EPSCs via
presynaptic nAChRs in L6A CT but not CC pyramidal cells. To
better understand the effects of ACh on intralaminar
synaptictrans mission, recordings were performed from
synaptically coupled L6A pyramidal cell pairs. We found that
ACh suppresses presynaptic release in neuronal microcircuits
with a presynaptic CCpyramidal cell via activation of M4Rs.
In marked contrast, ACh increased the release probability
inL6A connections with a presynaptic CT neuron through
activating nAChRs. Our results reveal that two functionally
and morphologically distinct subpopulations of L6A pyramidal
cells are affected differentially by ACh indicating that
intra- and subcortical signaling is subject to behavioural
modulation.},
cin = {535500-2 / 162320 / 160000},
ddc = {570},
cid = {$I:(DE-82)535500-2_20140620$ / $I:(DE-82)162320_20140620$ /
$I:(DE-82)160000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2018-230346},
url = {https://publications.rwth-aachen.de/record/749817},
}
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