Synaptic events of stellate and fan cells in layer II of the entorhinal cortex of the C57BL6J wild type mouse
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Citation
Abstract
Investigations into the superficial layers of the medial entorhinal cortex (MEC) and the lateral entorhinal cortex (LEC) have revealed that the projections from the two areas to the hippocampus play roles in distinct forms of memory. Differences between the two areas extend further and include differing extrinsic inputs and projection targets, morphological differences between principal cells, as well as electrophysiological characteristics. Synaptic events in principal cells of layer II of the entorhinal cortex (ECII) are also fundamentally different between areas and are crucial for eliciting and modulating firing activity in these cells. In the present study, synaptic events in stellate and fan cells of the MECII and LECII respectively, are compared. No differences in spontaneous excitatory postsynaptic currents (sEPSCs) were found between superficial MEC and LEC cells, however, when morphologically verified stellate and fan cells were compared, frequency, rise time, and decay time of sEPSCs were all significantly higher in stellate cells compared to fan cells. Additionally, spontaneous inhibitory postsynaptic currents (sIPSCs) differences were found between both MEC and LEC, as well as between stellate and fan cells. The main difference was seen in amplitude of events, where MEC cells had significantly higher amplitude sIPSCs than LEC cells. Specific comparisons of stellate vs fan cells also showed this difference, in addition to significantly higher values for area under the curve of sIPSCs in stellate cells. Importantly, high amplitude and area bursts of sEPSCs and sIPSCs could be readily seen in MEC cells and stellate cells, whereas few if any cells in the LEC exhibited bursts of synaptic activity. Further analysis of bursting behavior showed that these bursts were rhythmic in nature, and rhythmic bursts of both sEPSCs and sIPSCs could be seen frequently in the same cell at subsequential time points. These results point to further differences in MEC and LEC cells, with cells in layer II of the MEC receiving burst-like rhythmic postsynaptic current inputs, possibly due to greater temporal summation of coincident events. These events, particularly bursting postsynaptic currents, could maintain important functional differences in these two groups of cells, such as the noted grid cell behavior seen in cells of ECII in the MEC.
Description
2025
License
Attribution 4.0 International