A Characterization of the Electrophysiological and Morphological Properties of Vasoactive Intestinal Peptide (VIP) Interneurons in the Medial Entorhinal Cortex (MEC).

Saishree Badrinarayanan,Frédéric Manseau,Sylvain Williams,Mark P Brandon

doi:10.3389/fncir.2021.653116

Saishree Badrinarayanan, Frédéric Manseau + Show 2 more

Open Access

https://doi.org/10.3389/fncir.2021.653116

Copy DOI

Abstract

Circuit interactions within the medial entorhinal cortex (MEC) translate movement into a coherent code for spatial location. Entorhinal principal cells are subject to strong lateral inhibition, suggesting that a disinhibitory mechanism may drive their activation. Cortical Vasoactive Intestinal Peptide (VIP) expressing inhibitory neurons are known to contact other interneurons and excitatory cells and are thus capable of providing a local disinhibitory mechanism, yet little is known about this cell type in the MEC. To investigate the electrophysiological and morphological properties of VIP cells in the MEC, we use in vitro whole-cell patch-clamp recordings in VIPcre/tdTom mice. We report several gradients in electrophysiological properties of VIP cells that differ across laminae and along the dorsal-ventral MEC axis. We additionally show that VIP cells have distinct morphological features across laminae. Together, these results characterize the cellular and morphological properties of VIP cells in the MEC.

Highlights

The medial entorhinal cortex (MEC) is a six-layered cortical structure involved in episodic memory and spatial navigation
We found that a total of 6,219.56 ± 607.81 cells expressed tdTomato, of which 5,849.51 ± 633 cells were labeled with Vasoactive Intestinal Peptide (VIP) IHC (Figure 1C)
Using in vitro whole-cell patch-clamp recordings, we investigate the distribution, morphology, active and passive membrane properties of VIP interneurons in the MEC

Summary

Introduction

The medial entorhinal cortex (MEC) is a six-layered cortical structure involved in episodic memory and spatial navigation. Layers I-III form the input and layers V-VI form the output domain to various cortical structures (Ramsden et al, 2015; Sürmeli et al, 2015; Witter et al, 2017). Projections to the hippocampus from the MEC primarily originate from the superficial layers, while outputs from the hippocampus terminate in the deep MEC layers (Canto et al, 2008). Through these reciprocal connections, circuits within the hippocampus and the MEC support spatial navigation and memory (Moser et al, 2008). Grid cells fire in a repetitive hexagonal spatial pattern that spans the environment an animal navigates. It is because of these properties that grid cells are suggested to perform a function known as path integration (Mittelstaedt and Mittelstaedt, 1980; McNaughton et al, 2006)

Objectives

Methods

Results

Conclusion