Nonclassical Estrogen Modulation of Presynaptic GABA Terminals Modulates Calcium Dynamics in Gonadotropin-Releasing Hormone Neurons

Abstract

There is increasing recognition that estrogen exerts multifaceted regulatory effects on GnRH neurons. The acute effects of estrogen on calcium dynamics in these cells were examined using a transgenic mouse line that allows real-time measurement of intracellular calcium concentration ([Ca2+]i) in GnRH neurons in the acute brain slice preparation. 17-beta-Estradiol (E2) at 100 pm-100 nm was found to activate [Ca2+]i transients in approximately 40% of GnRH neurons with an approximate 15-min latency. This effect was not replicated by E2-BSA, which limits E2 action to the membrane, 17-alpha-estradiol, the inactive isomer at classical estrogen receptors (ERs), or G-1 the GPR30 agonist. E2 continued to activate [Ca2+]i transients when transcription was blocked. An ER alpha-selective agonist was equally potent in activating [Ca2+]i transients, and E2 remained effective in ERbeta knockout x GnRH-Pericam mice. E2's activation of [Ca2+]i transients continued in the presence of tetrodotoxin, which blocks action potential-dependent transmission, but was abolished completely by the further addition of a gamma-aminobutyric acid (GABA)A receptor antagonist. Exogenous GABA was found to initiate [Ca2+]i transients in GnRH neurons. Whole cell, voltage-clamp recordings of GnRH-green fluorescence protein neurons revealed that E2 generated discrete bursts of miniature inhibitory postsynaptic currents with a latency of approximately 15 min. These observations provide evidence for a new mechanism of nonclassical estrogen action within the brain. Estrogen interacts with the classical ERalpha at the level of the GABAergic nerve terminal to regulate action potential-independent GABA release that, in turn, controls postsynaptic calcium dynamics.

p21-Activated kinase mediates rapid estradiol-negative feedback actions in the reproductive axis

“…The localization of ERs to dendrites and axon terminals has been shown previously in hypothalamic neurons as well (56). Herbison and colleagues (57) have also recently characterized a nonclassical ER␣ signaling mechanism that mediates E 2 modulation of GABAergic transmission on GnRH neurons.…”

Two Slow Calcium-Activated Afterhyperpolarization Currents Control Burst Firing Dynamics in Gonadotropin-Releasing Hormone Neurons

“…The electrical properties and firing behavior of individual GnRH neurons are identical in GnRH-Pericam and GnRH-EGFP transgenic mice (K. Lee and A. E. Herbison, unpublished data). [Ca 2ϩ ] i was monitored in individual GnRH neurons as reported previously (Jasoni et al, 2007;Romanò et al, 2008) with slight modifications. In brief, excitation was performed by exposing slices to 415 nm wavelength for 100 ms every second using Sutter DG-4 highspeed filter unit.…”

Estradiol Shapes Auditory Processing in the Adult Brain by Regulating Inhibitory Transmission and Plasticity-Associated Gene Expression

“…The 17␤-estradiol, BIC, and DNQX were obtained from Sigma, TMX was purchased from Tocris Cookson, and ATD was from Steraloids. All compounds were diluted in DMSO, and their chosen concentrations were well within the standard range used in neuronal preparations (E2 at 50 nM, TMX at 2 M, and ATD at 20 M) (Wade et al, 1994;ChesnoyMarchais, 2003ChesnoyMarchais, , 2005Duncan, 2005;Nishimura et al, 2008;Romanò et al, 2008). For experiments involving blockade of aromatase activity, adjacent slices were either preincubated in aCSF containing ATD (experimental) or aCSF alone (control) for 30 min before the recording session.…”