Ovulation is triggered by a cyclical modulation of gonadotropes into a hyperexcitable state

Abstract

Gonadotropes in the anterior pituitary gland are essential for fertility and provide a functional link between the brain and the gonads. To trigger ovulation, gonadotrope cells release massive amounts of luteinizing hormone (LH). The mechanism underlying this remains unclear. Here, we utilize a mouse model expressing a genetically encoded Ca²⁺ indicator exclusively in gonadotropes to dissect this mechanism in intact pituitaries. We demonstrate that female gonadotropes exclusively exhibit a state of hyperexcitability during the LH surge, resulting in spontaneous [Ca²⁺]_i transients in these cells, which persist in the absence of any in vivo hormonal signals. L-type Ca²⁺ channels and transient receptor potential channel A1 (TRPA1) together with intracellular reactive oxygen species (ROS) levels ensure this state of hyperexcitability. Consistent with this, virus-assisted triple knockout of Trpa1 and L-type Ca²⁺ subunits in gonadotropes leads to vaginal closure in cycling females. Our data provide insight into molecular mechanisms required for ovulation and reproductive success in mammals.

Keywords: CP: Developmental biology; CRISPR; L-type Ca(2+) channels; ROS; TRPA1; adeno-associated virus; conditional knockout; genetic labeling; gonadotropes; ovulation; proestrus.