Gq Protein-Coupled Membrane-Initiated Estrogen Signaling Rapidly Excites Corticotropin-Releasing Hormone Neurons in the Hypothalamic Paraventricular Nucleus in Female Mice

Abstract

CRH neurons in the hypothalamic paraventricular nucleus (PVN) play a central role in regulating the hypothalamus-pituitary-adrenal (HPA) axis and are directly influenced by 17β-estradiol (E2). Although compelling evidence has suggested the existence of membrane-associated estrogen receptors (mERs) in hypothalamic and other central nervous system neurons, it remains unknown whether E2 impacts CRH neuronal excitability through this mechanism. The purpose of the current study is to examine the existence and function of mER signaling in PVN CRH neurons. Whole-cell recordings were made from CRH neurons identified by Alexa Fluor 594 labeling and post hoc immunostaining in ovariectomized female mice. E2 (100nM) rapidly suppressed the M-current (a voltage-dependent K(+) current) and potentiated glutamatergic excitatory postsynaptic currents. The putative Gq-coupled mER (Gq-mER) characterized in hypothalamic proopiomelanocortin neurons initiates a phospholipase C-protein kinase C-protein kinase A pathway; therefore, we examined the involvement of this pathway using selective inhibitors. Indeed, the ER antagonist ICI 182780 and inhibitors of Gq-phospholipase C-protein kinase C-protein kinase A blocked E2's actions, suggesting dependence on the Gq-mER. Furthermore, STX, a selective ligand for the Gq-mER, mimicked E2's actions. Finally, to examine the in vivo effect of Gq-mER activation, E2 or STX injection increased c-fos expression in CRH neurons in the PVN, suggesting CRH neuronal activation. This corresponded to an increase in plasma corticosterone. We conclude that the Gq-mER plays a critical role in the rapid regulation of CRH neuronal activity and the HPA axis. Our findings provide a potential underlying mechanism for E2's involvement in the pathophysiology of HPA-associated mood disorders.

Corticotropin-Releasing Hormone Signaling in the Oval Bed Nucleus of the Stria Terminalis Mediates Chronic Stress-Induced Negative Valence Behaviors Associated with Anxiety

“…Next, we determined the effects of CVMS on ovBNST electrophysiological properties using ex vivo slices (Fig.2A). We first measured M-currents (KCNQ/Kv7 channels), a subthreshold noninactivating voltage-dependent outward K + current that controls action potential generation and neuronal excitability (42), in ovBNST neurons using a standard deactivation-activation protocol over a voltage range (−75 to −25 mV) where M-currents have profound effects on neuronal excitability (Fig.2C). M-currents were calculated by determining current relaxation, the difference between the instantaneous and steady states (Fig.3C arrows).…”

Sex differences in stress responses: a critical role for corticotropin-releasing factor

“…Membrane estrogen receptors that initiate intracellular signaling cascades also can regulate CRF neurons. For example, estradiol increases the excitability of CRF neurons in the PVN via the activation of the putative Gq-coupled membrane estrogen receptor [116]. The effect of CRF on postsynaptic neurons can also be regulated by membrane estrogen receptors, such as the G protein-coupled estrogen receptor 1 (GPER1), which can form a heterodimer with CRF receptors [117].…”

17β-Estradiol Increases Arcuate KNDy Neuronal Sensitivity to Ghrelin Inhibition of the M-Current in Female Mice

“…Electrophysiology was performed as described previously [32,33,39]. In hypothalamic slices, standard whole-cell patch-clamp recording procedures and pharmacological testing were used.…”

“…Because the KCNQ channel current (M-current) in KNDy neurons have not been previously studied, we initially established M-current activity using the selective KCNQ channel blocker XE-991, 40 µM a dose based on previous investigation [32,39]. To establish efficacy, we performed current-clamp recordings from Tac2-EGFP neurons and applied XE-991 to the bath solution.…”

“…IP 3 is released into the cytosol and increases release of intracellular calcium from internal stores. DAG activates PKC that then either directly decreases KCNQ channel (M-current) conductance [27,31] or activates PKA [39]. To confirm the role of this pathway (PLC-PKC) in attenuating the M-current in Tac2 neurons, we applied a series of specific pharmacological interventions.…”