Estrogen has been known to modulate neural development for decades. The main focus of these effects has been on the traditional nuclear estrogen receptors, Estrogen Receptor-α (ERα) and Estrogen Receptor-β (ERβ). The discovery of the G Protein-Coupled Estrogen Receptor (GPER) suggests our knowledge of estrogen’s effects is incomplete. While evidence has suggested roles of GPER in the nervous system, most studies have looked only at effects in mature neurons, not embryonic neurons. Here we sought to study the role of GPER activity in neurite outgrowth, synapse formation, and signaling pathways GPER uses in rat embryonic neurons in two brain regions, the cortex and hippocampus.
All experiments were done using embryonic day 18 (E18) rat cortical and hippocampal neurons. Experimental treatments used vehicle (DMSO), a nonselective ER agonist (E2), a selective GPER agonist (G1), and/or a selective GPER antagonist (G15). Neurite growth was measured at multiple time points using the ImageJ plugin NeuronJ. Synapses were visualized at 7-20 days in culture. Network activity was measured in neurons cultured on a multi-electrode array. Signaling pathway experiments were performed using Fura-2 AM ratiometric calcium imaging technique. Our data revealed that activation of GPER induced brain-region specific effects on neurite outgrowth, promoting neurite growth in hippocampal neurons, while having variable effects on outgrowth of cortical neurons. We also found that activation of GPER did not affect synapse formation in hippocampal and cortical neurons, but increases network activity in both brain regions. Furthermore, our data showed that GPER activation by G1 significantly increased internal calcium levels in hippocampal, but not cortical neurons. Finally we demonstrated that the G1-induced rise in intracellular calcium in hippocampal neurons involves a PLC/IP3R-mediated internal calcium pathway and a cAMP-independent PKA calcium entry pathway. Together, our data provide evidence that GPER activation may play different roles in brain regions during early development. Additionally, this work shed novel insights into the possible involvement of second messengers and protein kinase pathways in GPER actions on early neural development. Information from this thesis work is fundamental to our understanding of the roles and acting mechanisms of GEPR during early nervous system development.
|Commitee:||Arnatt, Christopher, Ogilvie, Judith, Spencer, Susan, Wang, Yuqi|
|School:||Saint Louis University|
|School Location:||United States -- Missouri|
|Source:||MAI 81/12(E), Masters Abstracts International|
|Subjects:||Neurosciences, Developmental biology, Cellular biology|
|Keywords:||Calcium, Estrogen, GPER, IP3, Neurite, Neuron|
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