SAT-031 GnRH Firing For Food And Fertility

Abstract N.D. Mansano: None. J. Kearney: None. S. Wray: None. GnRH neurons are essential for fertility, a process modulated by numerous extrinsic and intrinsic cues. As such, GnRH neurons integrate incoming signals from a wide range of systems to ensure reproductive success. GnRH neurons express receptors related to food intake, such as, the orexigenic hormone Neuropeptide Y (NPY) and anorexigenic hormone proopiomelanocortin (POMC), potentially linking metabolic function and reproduction. Although it has been reported that GnRH neurons respond independently to NPY and α-melanocyte-stimulating hormone (α-MSH, product from POMC) in adult mice, it’s unclear how these circuit might interact. This study examines the relationship between α-MSH and NPY signaling in GnRH neurons using calcium imaging of GnRH cells maintained in explants and in situ loose-cell patch-clamp recordings in brain slices from GnRH-GFP mice at different reproductive stages: prepubertal (PN10), pubertal (PN35) and adult male and female mice (PN 60-90). In addition, immunocytochemical analysis will be performed at the same stages to determine the expression of NPY receptors (Y1R, Y4R) and α-MSH receptors (MC4, MC1) in GnRH cells, receptors so far identified in GnRH neurons. For both calcium imaging electrophysiological experiments, an amino acid blocker (AAB) was added after the first serum-free media or artificial cerebrospinal fluid period to help delineate direct from indirect responses via interneurons. The AAB contains inhibitors to ionotropic glutamatergic receptors (-Cyano-7-nitroquinoxaline-2,3-dione (CQNX, 10µM), D-2-Amino-5-phospho-nopentanoic acid (D-AP5, 10µM)) and GABAA receptors (-Bicuculline methiodide (BIC, 10µM). To date, results indicate that calcium oscillations decreased in the majority of GnRH cells in explants, devoid of brain, consistent with the literature. Notably, after 5 min washout ∼22% of the GnRH cells responded with an increase in activity to α-MSH (50nM, n=90 cells/2 explants). Electrophysiological recordings show that in slices from pubertal mice α-MSH increases activity (♀n=12 cells/3mice); ♂n=10 cells/3 mice) but not in slices from adult males (♂n=10 cells/4 mice). Suggesting that pubertal mice are more sensitive to the anorexigenic hormone α-MSH, consistent with the fact that puberty is accompanied by an increase in food intake and change in body weight. Currently, we are delineating the effects of α-MSH in adult females at different stages of the estrous cycle and will use receptor agonists and antagonists to determine the inter-play between metabolic cues on GnRH neuronal activity. Saturday, June 1, 2024