Varying Effects of the G‐Protein Coupled Estrogen Receptor During Development in Embryonic Rat Hippocampal and Cortical Neurons

Abstract

Estrogen has been known to play a role in enhancing brain development for over half a century. Most studies of estrogen's effect on the nervous system have focused on the traditional estrogen receptors Estrogen Receptor‐α (ERα) and Estrogen Receptor‐β (ERβ). The recent discovery of the G‐Protein Coupled Estrogen Receptor (GPER) suggests knowledge of estrogen's effects may be incomplete. While evidence has suggested the roles GPER plays in the nervous system include neuroprotection, neuronal recovery from stroke and degeneration, neuron proliferation, as well as many others. A caveat is that most studies have looked only at the effect in mature neurons and not the effect GPER has during early neuronal development. Here we sought to study the role of GPER activity in neurite outgrowth and synapse formation during early development.Embryonic day 18 rat cortical and hippocampal neurons were cultured in estrogen‐ and phenol red‐ free medium in the presence of a nonselective ER agonist (E2), a selective GPER agonist (G‐1), and a selective GPER antagonist (G‐15). Neurite growth was measured at 20, 48, 72, and 96 hours in culture using the ImageJ plugin NeuronJ. Synapses were visualized at 7 and 14 days in culture by using immunofluorescence of the pre‐ and post‐synaptic markers, synaptophysin and PSD‐95, respectively. Synapse formation was measured by measuring the overlap between these markers in ImageJ. Our data revealed activation of GPER promoted neurite growth in hippocampal neurons, but not in cortical neurons, but blocking the receptor inhibited neurite growth in cortical neurons. In addition, low levels of G1 (1μM) inhibited neurite outgrowth in cortical neurons. Cortical neurons showed no significant difference in synapse formation, while in hippocampal neurons the effect varied based on time period and dosage. This provides the first evidence that GPER activation may play different roles in brain regions, as well as having specific dosage based effects in specific regions. Future experiments will investigate the molecular and cellular mechanisms underlying the pharmacological differences in GPER effects between developing cortical and hippocampal neurons.Support or Funding InformationThis project was supported by the Saint Louis University Start‐up Fund for Dr. Xu lab and the Sigma XI Grant‐In‐Aid of Research awarded to Mr. Kyle Pemberton.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.