Role of GPR30 in Mediating Estrogen Effects on Neurons and Cognitive Performance

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DESCRIPTION (provided by applicant): Basic and clinical research suggests loss of estradiol following menopause may contribute to brain aging and increased risk of age-related cognitive decline and dementia. There is a great need for novel estrogenic compounds that confer positive cognitive effects without risk of side effects. G-1 is a recently developed agonist for the novel transmembrane estrogen receptor (ER) GPR30 [1]. Activation ofthe GPR30 pathway is independent of either of the classical ER a or p pathways, raising the possibility of using G-1 as a novel estrogenic agent that lacks the risks associated with other estrogenic compounds. Previous work in our laboratory has shown that estradiol enhances cognitive performance in rats via effects on basal forebrain cholinergic neurons [13]. We hypothesize that the effects of estradiol on cholinergic function and cognitive performance are mediated, in part, via effects on GPR30. The first goal is to characterize GPR30 expression in the rat forebrain, focusing on co-expression by cholinergic neurons. Preliminary data show extensive co- localization of GPR30 within cholinergic neurons in the septum, digonal band of Broca, and nucleus basils. Because use of the GPR30 antibody on brain tissues is relatively new, GPR30 mRNA expression will also be evaluated using laser capture microscopy and RT-PCR. The second goal is to examine the functional effects of GPR30 activation on the cholinergic neurons. Estradiol has been shown to induce activation of Erk and CREB in brain neurons, including basal forebrain cholinergic neurons. Estradiol also has been shown to increase potassium-stimulated acetylcholine release in the hippocampus, consistent with an effect on basal forebrain cholinergic function. Our studies will evaluate rapid induction of pCREB and pEri< within ChAT- positive cells in response to systemic and ICV infusions of G-1 and other selective ER agonists. In vivo microdialysis will evaluate the effects of selective ER agonists on acetylcholine release in the hippocampus. The third goal is to test the ability of G-1 to enhance cognitive performance in ovariectomized rats comparable to the effects of estradiol. Effects of G-1 and estradiol will be compared with selective ER a and Q, agonists. Preliminary data suggest G-1 reverses effects of ovariectomy on acquisition of a delayed matching-to-position T-maze task, similar to the effects of estradiol. Public Health Significance: Following menopause, women lose the neuroprotective effects of estrogen, placing them at an increased risk of developing age related cognitive decline and Alzheimer's Disease, destructive neurological conditions for which no cure currently exists. Our analyses may broaden the understanding of a new pathway of estrogen signaling, laying groundwork for the development of a new form of therapy for these diseases.