Effect of bacterial endotoxin on migration of gonadotropin-releasing hormone-producing neurons in rat embryogenesis

The effect of bacterial lipopolysaccharide endotoxin (LPS), immune system activator, on differentiation and migration of gonadotropin-releasing hormone-producing neurons in rat embryogenesis has been studied. Intraperitoneal injection with LPS (18 μg/kg) into pregnant rats on the 12th day of pregnancy led to 50% decrease in total number of GnRH-neurons in the forebrain of 17-day-old embryos and 17% decrease in 19-day-old embryos. At the same time, the number of GnRH-neurons in the nasal area of the head of 17- and 19-day-old embryos was increased by 40 and 50%, respectively, whereas it increased by 20% in olfactory bulbs of 17-day-old embryos and was not changed in olfactory bulbs of 19-day-old embryos. Neither the total number of neurons nor their distribution patterns were affected by LPS injection into pregnant rats on the 15th day of pregnancy. Singular localization of GnRH-neurons in embryo forebrain was observed after LPS administration, whereas the neurons were located by groups of 3–4 cells in rostral areas. Therefore, at the early stages of pregnancy, LPS was shown to suppress initial stages of differentiation and migration of GnRH-producing neurons. The effects observed in our study may be mediated by LPS-induced proinflammatory cytokines.