Ethanolamine plasmalogens increase luteinising hormone pulsatility and are associated with GPR61 expression in bovine gonadotrophin‐releasing hormone neurons

Abstract Pulsatile secretion of luteinising hormone (LH) reflects episodic activity of hypothalamic gonadotrophin‐releasing hormone (GnRH) neurons and is essential for reproductive function. Plasmalogens are ether phospholipids enriched in neuronal membranes; however, their role in neuroendocrine regulation of reproduction remains unclear. We examined the effects of ethanolamine and choline plasmalogens on LH pulsatility in vivo and investigated GPR61 expression in bovine hypothalamic tissues and relevant cell lines. The oestrous cycles of 15 Holstein heifers were synchronised, and blood samples were collected at 10 min intervals for 8 h. Ethanolamine plasmalogens, choline plasmalogens or vehicle were administered intravenously. LH concentrations were measured by radioimmunoassay, and LH pulses were identified using the Pulsar algorithm. GPR61 expression was examined by RT‐PCR, Western blotting and immunofluorescence in bovine hypothalamic tissues and in cell lines. LH pulse frequency showed a significant treatment × time interaction ( p < .01) and increased after ethanolamine plasmalogen administration (Holm‐adjusted p = .0084), whereas no significant changes were observed after choline plasmalogen or control treatments. Mean LH concentrations showed a significant effect of time ( p < .01), whereas neither the treatment effect nor the treatment × time interaction was significant. LH pulse amplitude was unaffected. GPR61 was expressed in GnRH neurons in the bovine hypothalamus, including the preoptic area, arcuate nucleus and median eminence, and was also detected in GT1‐7 and LβT2 cells. Ethanolamine plasmalogens are associated with increased LH pulsatility in vivo and GPR61 expression in GnRH neurons, suggesting a potential role for plasmalogen composition in the neuroendocrine regulation of reproduction.