The long-term goal of this project is to determine the neurobiological mechanisms that underlie the effects of estrogens on the adult hypothalamo-pituitary-adrenal (HPA) axis. HPA axis activation in mammals is a basic response to environmental perturbations that threaten homeostasis and such responses, although beneficial in the short-term, have deleterious consequences under chronic conditions. Prolonged elevations of adrenal glucocorticoids (GCs) are neuroendangering and alter feeding and autonomic functions. Moreover, a dysregulation of the HPA activity accompanies these disorders. In rodents, females show a more robust HPA axis response to stress than do males, partly because of sex-differences in circulating estradiol (E2) levels. Thus, the overarching postulate of this application is that individual differences in adult stress-responses arise from differential E2 actions on the stress-circuitry. Our studies focus predominantly on estrogen receptor beta (ER?). Rodent studies show that the alpha form of ER (ER?) increases adrenal corticosterone (CORT) and the pituitary adrenocorticotropic hormone (ACTH) response to stressors whereas activation of ER? inhibits HPA activity. Importantly, ER? is highly expressed in neurons of the PVN of both male and female mice to allow integration of gonadal hormone levels with stress-related inputs. Using novel transgenic mouse models, we will identify stress responsive ER?-ergic neural circuitry of the mouse hypothalamus and determine how activation of PVN ER? reduces HPA drive and energy balance.
Specific aim 1 will determine if OT is required for ER? regulation of PVN function using a novel Oxytocin:cre recombinase mouse line and an ER?-cre mouse line to genetically manipulate OT and ER? neurons.
Aim 2 will assess the function of ER? neurons that are incorporated into the stress circuitry of the mouse brain following multimodal stress and chronic unpredictable mild stressors.
Aim 3 will elucidate molecular changes and sex differences that occur in PVN ER? neurons in response to MMS and to glucocorticoids. In all cases we are highly cognizant of the presence of sex differences in these physiological pathways and will explore the role that estradiol or 5?-androstan 3?,17? diol (3? diol), a metabolite of the androgen, dihydrotestosterone that binds and activates ER?, have on HPA axis activation and feeding behaviors. The results of these studies will provide novel insight into the role played by PVN ER? neurons in controlling hypophysiotrophic function and metabolism with hopes of identifying novel targets for therapeutic approaches to treating stress and associated neurological deficits.

Public Health Relevance

Estrogens regulate the activity of the hypothalamic-pituitary-adrenal axis through estrogen receptors to allow integration of reproductive information within stress-related circuitry, thereby fine tuning neuroendocrine stress responses and metabolic processes, including feeding and weight gain. In these studies we will test the hypothesis that estrogen receptor beta neurons influence the HPA axis through local circuit interactions with oxytocin to inhibit hormonal responses to stress along with feeding behaviors. Our studies will use novel mouse models to modify the expression or activity of estrogen receptor beta in oxytocin neurons that are integrated into the stress circuitry (aim 1), explore the identity of ER? neurons that are altered by chronic unpredictable mild stress (aim 2) and define the molecular mechanisms in ER? and OT neurons of the PVN whereby these changes can occur (aim 3).

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
2R01DK105826-06
Application #
9839334
Study Section
Integrative and Clinical Endocrinology and Reproduction Study Section (ICER)
Program Officer
Malozowski, Saul N
Project Start
2015-04-05
Project End
2021-08-31
Budget Start
2019-09-13
Budget End
2020-08-31
Support Year
6
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Colorado State University-Fort Collins
Department
Veterinary Sciences
Type
Schools of Veterinary Medicine
DUNS #
785979618
City
Fort Collins
State
CO
Country
United States
Zip Code
80523
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