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A barrel-related interneuron in layer 4 of rat somatosensory cortex with a high intrabarrel connectivity.

Koelbl C, Helmstaedter M, Lübke J, Feldmeyer D - Cereb. Cortex (2013)

Bottom Line: Three distinct clusters of FS L4 interneurons were identified based on their axonal morphology relative to the barrel column suggesting that these neurons do not constitute a homogeneous interneuron population.We found on average 3.7 ± 1.3 putative inhibitory synaptic contacts that were not restricted to perisomatic areas.In conclusion, we characterized a novel type of barrel cortex interneuron in the major thalamo-recipient layer 4 forming dense synaptic networks with L4 spiny neurons.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Physiology, Max Planck Institute of Medical Research, Jahnstr. 20, D-69120 Heidelberg, Germany Current address: Section of Cardiovascular Medicine, Boston University Medical Center, 88 East Newton Street, Boston, MA 02118, USA.

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Identification of synaptic contacts. (A) Low-power photomontage of a synaptically connected pair of a BIn and a spiny stellate cell that were filled with biocytin during recording. The 2 neurons showed reciprocal coupling. Putative, light microscopically identified GABAergic synaptic contacts between the presynaptic L4 interneuron (left) and the postsynaptic spiny stellate cell (right) are marked by green dots. Putative reciprocal excitatory synaptic contacts are indicated by blue dots. Asterisks highlight long axonal collaterals of the spiny stellate cell. (A1–5) High-power images of synaptic contacts. Blue open circles, inhibitory contacts (A1–3); green open circles, excitatory contacts (A4 and A5). (B) Neurolucida reconstruction of the same neuron pair shown in (A). Blue, L4 interneuron axon; red, L4 interneuron soma and dendrite; green, L4 spiny stellate axon; white, L4 spiny stellate soma and dendrite. The inset shows the dendritic arbor of pre- and postsynaptic neuron together with the putative synaptic contacts (same color code as for panel A).
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BHT263F6: Identification of synaptic contacts. (A) Low-power photomontage of a synaptically connected pair of a BIn and a spiny stellate cell that were filled with biocytin during recording. The 2 neurons showed reciprocal coupling. Putative, light microscopically identified GABAergic synaptic contacts between the presynaptic L4 interneuron (left) and the postsynaptic spiny stellate cell (right) are marked by green dots. Putative reciprocal excitatory synaptic contacts are indicated by blue dots. Asterisks highlight long axonal collaterals of the spiny stellate cell. (A1–5) High-power images of synaptic contacts. Blue open circles, inhibitory contacts (A1–3); green open circles, excitatory contacts (A4 and A5). (B) Neurolucida reconstruction of the same neuron pair shown in (A). Blue, L4 interneuron axon; red, L4 interneuron soma and dendrite; green, L4 spiny stellate axon; white, L4 spiny stellate soma and dendrite. The inset shows the dendritic arbor of pre- and postsynaptic neuron together with the putative synaptic contacts (same color code as for panel A).

Mentions: Putative synaptic contacts for all reconstructed biocytin-labeled inhibitory L4 interneuron–L4 spiny neuron pairs were identified by light-microscopic examination (magnification ×100 objective and ×10 eyepiece; see Fig. 6, cf., Markram et al. 1997). In previous publications, we have shown using electron microscopic analysis that this allows a reliable identification of synaptic contacts established by presynaptic axons on postsynaptic dendrites (cf., Markram et al. 1997; Feldmeyer et al. 2002, 2006; Silver et al. 2003).Figure 6.


A barrel-related interneuron in layer 4 of rat somatosensory cortex with a high intrabarrel connectivity.

Koelbl C, Helmstaedter M, Lübke J, Feldmeyer D - Cereb. Cortex (2013)

Identification of synaptic contacts. (A) Low-power photomontage of a synaptically connected pair of a BIn and a spiny stellate cell that were filled with biocytin during recording. The 2 neurons showed reciprocal coupling. Putative, light microscopically identified GABAergic synaptic contacts between the presynaptic L4 interneuron (left) and the postsynaptic spiny stellate cell (right) are marked by green dots. Putative reciprocal excitatory synaptic contacts are indicated by blue dots. Asterisks highlight long axonal collaterals of the spiny stellate cell. (A1–5) High-power images of synaptic contacts. Blue open circles, inhibitory contacts (A1–3); green open circles, excitatory contacts (A4 and A5). (B) Neurolucida reconstruction of the same neuron pair shown in (A). Blue, L4 interneuron axon; red, L4 interneuron soma and dendrite; green, L4 spiny stellate axon; white, L4 spiny stellate soma and dendrite. The inset shows the dendritic arbor of pre- and postsynaptic neuron together with the putative synaptic contacts (same color code as for panel A).
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Related In: Results  -  Collection

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BHT263F6: Identification of synaptic contacts. (A) Low-power photomontage of a synaptically connected pair of a BIn and a spiny stellate cell that were filled with biocytin during recording. The 2 neurons showed reciprocal coupling. Putative, light microscopically identified GABAergic synaptic contacts between the presynaptic L4 interneuron (left) and the postsynaptic spiny stellate cell (right) are marked by green dots. Putative reciprocal excitatory synaptic contacts are indicated by blue dots. Asterisks highlight long axonal collaterals of the spiny stellate cell. (A1–5) High-power images of synaptic contacts. Blue open circles, inhibitory contacts (A1–3); green open circles, excitatory contacts (A4 and A5). (B) Neurolucida reconstruction of the same neuron pair shown in (A). Blue, L4 interneuron axon; red, L4 interneuron soma and dendrite; green, L4 spiny stellate axon; white, L4 spiny stellate soma and dendrite. The inset shows the dendritic arbor of pre- and postsynaptic neuron together with the putative synaptic contacts (same color code as for panel A).
Mentions: Putative synaptic contacts for all reconstructed biocytin-labeled inhibitory L4 interneuron–L4 spiny neuron pairs were identified by light-microscopic examination (magnification ×100 objective and ×10 eyepiece; see Fig. 6, cf., Markram et al. 1997). In previous publications, we have shown using electron microscopic analysis that this allows a reliable identification of synaptic contacts established by presynaptic axons on postsynaptic dendrites (cf., Markram et al. 1997; Feldmeyer et al. 2002, 2006; Silver et al. 2003).Figure 6.

Bottom Line: Three distinct clusters of FS L4 interneurons were identified based on their axonal morphology relative to the barrel column suggesting that these neurons do not constitute a homogeneous interneuron population.We found on average 3.7 ± 1.3 putative inhibitory synaptic contacts that were not restricted to perisomatic areas.In conclusion, we characterized a novel type of barrel cortex interneuron in the major thalamo-recipient layer 4 forming dense synaptic networks with L4 spiny neurons.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Physiology, Max Planck Institute of Medical Research, Jahnstr. 20, D-69120 Heidelberg, Germany Current address: Section of Cardiovascular Medicine, Boston University Medical Center, 88 East Newton Street, Boston, MA 02118, USA.

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Related in: MedlinePlus