A barrel-related interneuron in layer 4 of rat somatosensory cortex with a high intrabarrel connectivity.
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.
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.Show MeSH
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Mentions: The mean number of inhibitory contacts established by L4 FS interneurons onto L4 spiny neurons was 3.5 ± 1.2 (n = 17), ranging from 2 to 6 per connection (Fig. 7A inset, open bars). An analysis including only BIns gave almost identical values (3.7 ± 1.3 synaptic contact sites ranging from 2 to 6; n = 10; Figs 6 and 7A inset, filled bars). The geometric distance of each individual synaptic contact between the contact site on the postsynaptic dendrite and the postsynaptic soma was 64 ± 32 µm (range 3 to 126 µm, n = 59 contacts; Fig. 7A, open bars) for all inhibitory synaptic contacts from clusters 1–3 L4 interneurons. For BIn–L4 spiny neuron pairs, the contact to soma distance was 66 ± 32 µm (n = 37 contacts; Fig. 7A, filled bars). In accordance with their rather distant dendritic location, most contact sites were found on third-order dendrites of the postsynaptic L4 spiny neurons (for distribution of contact sites, see Table 2). No correlation between the number of synaptic contacts and the unitary IPSP amplitude at an individual GABAergic connection was observed. Furthermore, the number of inhibitory synaptic contacts per connection was not correlated with the distance between the somata of pre- and postsynaptic neurons for the BIn to L4 spiny neuron connection (Fig. 7B).Figure 7.
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.