# mGluR5 in Pyramidal Neurons in the Hippocampus Mediates Chronic Stress‐Induced Memory Deficits

## TL;DR

This study shows that mGluR5 in hippocampal neurons plays a key role in chronic stress-induced memory problems and suggests potential treatments.

## Contribution

The study identifies mGluR5 as a mediator of chronic stress-induced memory deficits and proposes CDPPB and PACAP as therapeutic strategies.

## Key findings

- Chronic stress reduces mGluR5 levels and impairs synaptic inputs in the hippocampus.
- Enhancing mGluR5 activity with CDPPB reverses stress-induced memory deficits.
- PACAP downregulation contributes to synaptic impairments, and its application can restore function.

## Abstract

Chronic stress causes variable profiles of physiological deficits, including mood disorders, sleep disorders, and memory deficits. However, the neural mechanisms and potential drug targets of chronic stress‐induced memory deficit remain elusive.

This study aimed to explore the function and regulatory mechanisms of metabotropic glutamate receptor 5 (mGluR5) in chronic stress‐induced memory deficit and investigate the potential therapeutic target for stress‐related memory deficit.

Behavioral tests were used to assess the effects of chronic stress on memory. Electrophysiological recordings were conducted to examine the synaptic inputs after chronic stress. RNA sequencing was employed to achieve transcriptional alterations in the hippocampus after stress or mGluR5 knockdown. Enrichment analysis was performed to identify the downstream effector of chronic stress‐induced memory deficits.

Chronic restraint stress (CRS) impairs hippocampal‐dependent memory and electrophysiological recordings reveal that chronic stress impairs synaptic inputs. Subsequently, we observe that the mGluR5 level declines after CRS, which is an important molecule for learning and memory. mGluR5 knockdown induces memory deficits and impairs synaptic inputs. Enhancement of mGluR5 activity by CDPPB could restore chronic stress‐induced memory deficits and rescue impaired synaptic inputs. Furthermore, we identify that pituitary adenylyl cyclase activating peptide (PACAP) is down‐regulated after CRS and mGluR5 knockdown. PACAP application could restore the impaired inhibitory synaptic inputs after CRS.

These results illuminate that the mGluR5 mediates chronic stress‐induced memory deficits, which may provide promising strategies for treating stress‐related memory deficits.

Diagrammatic representation of the role of mGluR5 in controlling memory impairments brought on by chronic stress. Chronic stress caused memory impairment, decreased GABAergic synaptic inputs, and decreased mGluR5 and PACAP levels in the hippocampus CA1. CDPPB restored memory damage by reversing the decline in GABAergic synaptic inputs caused by the stress. The reduction in GABAergic synaptic inputs brought on by chronic stress could also be reversed by PACAP administration.