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.

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.

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