# RFRP Neurons Are Required for Acute Stress-induced Suppression of the Estrogen-stimulated LH Surge in Female Mice

## TL;DR

This study shows that RFRP neurons are essential for stress to block the LH surge in female mice, a key step in reproduction.

## Contribution

The study identifies RFRP neurons as mediators of stress-induced suppression of the estrogen-stimulated LH surge in mice.

## Key findings

- RFRP neuron-ablated mice did not show stress-induced suppression of the LH surge.
- Acute restraint stress suppressed the LH surge in control mice but not in RFRP-ablated mice.
- Stress inhibited kisspeptin neuronal activation in the anteroventral periventricular region.

## Abstract

The association between perceived stress and reproductive dysfunction is known, yet the underlying mechanisms remain incompletely determined. We previously demonstrated that RF-amide related (RFRP) peptide 3-expressing neurons, putative inhibitors of the central regulation of fertility, are required for both acute restraint stress- and glucocorticoid-induced suppression of LH pulsatility in female mice. The present study complemented this by testing the role of RFRP neurons in the stress-induced suppression of the estrogen-induced preovulatory-like LH surge. We first established a reliable model of acute restraint stress in mice that stimulates glucocorticoid secretion, suppresses a late afternoon estrogen-induced LH surge, and inhibits corresponding kisspeptin neuronal activation in the anteroventral periventricular brain region. Two hours of restraint stress initiated 2 to 6 hours prior to lights off met these criteria. We then ablated RFRP neurons in adult female mice by expressing a diphtheria toxin receptor specifically in these cells and exposing them to diphtheria toxin. RFRP neuron-ablated and control mice that were ovariectomized and estrogen-treated were exposed to the acute, mid-afternoon restraint stress protocol and assessed for their peak LH concentrations several hours later at the expected time of the LH surge. Control mice exhibited stress-induced suppression of the LH surge, as expected, whereas RFRP-ablated mice did not. No differences in peak LH concentrations were observed between nonstressed controls and stressed RFRP-ablated mice. These data suggest that acute psychosocial stress occurring several hours prior to preovulatory LH surge induction invokes RFRP neuron-mediated blockade of the surge. The neural circuitry involved remains to be fully characterized.