Progesterone Treatment Inhibits and Dihydrotestosterone (DHT) Treatment Potentiates Voltage-Gated Calcium Currents in Gonadotropin-Releasing Hormone (GnRH) Neurons

• Published in: Endocrinology (Philadelphia) Vol. 151; no. 11; pp. 5349 - 5358
• Main Authors: Sun, Jianli, Moenter, Suzanne M
• Format: Journal Article
• Language: English
• Published: Chevy Chase, MD Endocrine Society 01.11.2010; The Endocrine Society
• Subjects: Analysis of Variance; Animals; Biological and medical sciences; Calcium - metabolism; Calcium Channels - metabolism; Dihydrotestosterone - pharmacology; Electrophysiology; Estradiol - pharmacology; Female; Fundamental and applied biological sciences. Psychology; Gonadotropin-Releasing Hormone - metabolism; Membrane Potentials - drug effects; Membrane Potentials - physiology; Mice; Mice, Transgenic; Neurons - drug effects; Neurons - physiology; Ovariectomy; Progesterone - pharmacology; Synaptic Transmission - drug effects; Vertebrates: endocrinology; Calcium; Gonadotropin RH; Ionic current; Inorganic element; Ovarian hormone; Progestagen; Hypothalamic hormone; Dihydrotestosterone; Neuron; Treatment; Progesterone; Hormone releasing factor; Sex steroid hormone
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/en.2010-0385

GnRH neurons are central regulators of fertility, and their activity is modulated by steroid feedback. In normal females, GnRH secretion is regulated by estradiol and progesterone (P). Excess androgens present in hyperandrogenemic fertility disorders may disrupt communication of negative feedback signals from P and/or independently stimulate GnRH release. Voltage-gated calcium channels (VGCCs) are important in regulating excitability and hormone release. Estradiol alters VGCCs in a time-of-day-dependent manner. To further elucidate ovarian steroid modulation of GnRH neuron VGCCs, we studied the effects of dihydrotestosterone (DHT) and P. Adult mice were ovariectomized (OVX) or OVX and treated with implants containing DHT (OVXD), estradiol (OVXE), estradiol and DHT (OVXED), estradiol and P (OVXEP), or estradiol, DHT, and P (OVXEDP). Macroscopic calcium current (ICa) was recorded in the morning or afternoon 8–12 d after surgery using whole-cell voltage-clamp. ICa was increased in afternoon vs. morning in GnRH neurons from OVXE mice but this increase was abolished in cells from OVXEP mice. ICa in cells from OVXD mice was increased regardless of time of day; there was no additional effect in OVXED mice. P reduced N-type and DHT potentiated N- and R-type VGCCs; P blocked the DHT potentiation of N-type-mediated current. These data suggest P and DHT have opposing actions on VGCCs in GnRH neurons, but in the presence of both steroids, P dominates. VGCCs are targets of ovarian steroid feedback modulation of GnRH neuron activity and, more specifically, a potential mechanism whereby androgens could activate GnRH neuronal function. Circulating steroid hormones regulate voltage-gated calcium currents in GnRH neurons as a component of the mechanism for steroid feedback.