Estradiol regulates voltage-gated potassium currents in corticotropin-releasing hormone neurons

Corticotropin-releasing hormone (CRH) neurons are the primary neural population controlling the hypothalamic–pituitary–adrenal (HPA) axis and the secretion of adrenal stress hormones. Previous work has demonstrated that stress hormone secretion can be regulated by circulating levels of estradiol. However, the effect of estradiol on CRH neuron excitability is less clear. Here, we show that chronic estradiol replacement following ovariectomy increases two types of potassium channel currents in CRH neurons: fast inactivating voltage-gated A-type K(+) channel currents (I(A)) and non-inactivating M-type K(+) channel currents (I(M)). Despite the increase in K(+) currents following estradiol replacement, there was no overall change in CRH neuron spiking excitability assessed with either frequency–current curves or current ramps. Together, these data reveal a complex picture whereby ovariectomy and estradiol replacement differentially modulate distinct aspects of CRH neuron and HPA axis function.