Neurotensin Regulates Primate Ovulation Via Multiple Neurotensin Receptors

Neurotensin (NTS), a small neuropeptide, was recently established as a key paracrine mediator of ovulation. NTS mRNA is highly expressed by granulosa cells in response to the luteinizing hormone surge, and multiple NTS receptors are expressed by cells of the ovulatory follicle. To identify the role of NTS receptors NTSR1 and SORT1 in ovulation in vivo, the dominant follicle of cynomolgus macaques (Macaca fascicularis) was injected with either vehicle control, the general NTS receptor antagonist SR142948, the NTSR1-selective antagonist SR48692, or the SORT1-selective antagonist AF38469. hCG was then administered to initiate ovulatory events. Ovulation was successful in all control-injected follicles. Rupture sites were smaller or absent after injection with NTS receptor antagonists. Histological analysis of follicles injected with SR142948, SR48692, or AF38469 revealed increased red blood cell extravasation and pooling in the follicle antrum when compared to controls. NTS receptor antagonist-injected follicles also showed dysregulated capillary formation and reduced luteinization of the granulosa cell layer. Prior in vitro studies showed that NTS significantly increased monkey ovarian microvascular endothelial cell (mOMEC) migration, while decreasing monolayer permeability. The NSTR1 antagonist SR48692 or siRNA knockdown of NTSR1 abrogated the ability of NTS to stimulate mOMEC migration and to decrease monolayer permeability. Similar experiments performed with the SORT1 antagonist AF38469 or siRNA knockdown of SORT1 also resulted in ablation of NTS-mediated changes in migration and permeability after SORT1 signaling was impaired. Together, these data implicate both NTSR1 and SORT1 to be critical mediators of NTS-stimulated ovulation, luteinization, and angiogenesis of the ovulatory follicle.