Glucagon-like peptide-1 control of GnRH secretion in female sheep

The role of glucagon-like peptide-1 (GLP-1) on gonadotropin-releasing hormone (GnRH) secretion was investigated in ovariectomised (OVX) ewes, which GnRH and luteinising (LH) had been restrained by treatment with oestrogen progesterone. Guide tubes for microinjection were placed above the median eminence (ME) animals allowed to recover 1 month. Jugular venous blood samples taken via cannulae at 10 min intervals. Vehicle (50 nL) injected into ME 2 h, followed injection GLP-1 ((7-36)-amide – 0.5 or nmol) its receptor agonist, exendin-4 (0.5 4 h ( n = 5). Plasma LH levels quantified as a surrogate measure secretion. elicited large amplitude pulse jugular plasma, effect greater higher dose. Exendin-4 caused large, sustained increase plasma levels. To determine how might exert an secretion, we employed double labelled situ hybridisation, RNAScope, co-localisation (GLP-1R) GnRH, Kisspeptin NPY cells hypothalami three ewes luteal phase estrous cycle. GLP1R expression clearly visible but not expressed GNRH1 expressing neurons visualised <5% KISS1 neurons. We conclude that may act level secretory terminals stimulate pathway through such is manifested remains unknown.