Effect of metronidazole on neural tube development in early chick embryos

Neural tube defect is the second most common type of congenital anomaly after congenital heart diseases. Although the exact cause is not clearly known, environmental and genetic factors have been shown to have an impact. Metronidazole is a drug that is used as an antibiotics and has effects on the central nervous system and peripheral nervous system. The aim of this study is to investigate the effects of different doses of metronidazole on neural tube development in a chick embryo model, which is similar to first month development in mammals. In this study, 60±5 gr. 100 white, fertile and 0-day-old SPF (specific pathogen free) eggs were used. These eggs, provided with appropriate temperature and humidity conditions, were incubated for 24 to 28 hours and then divided into four groups, including the control group. Metronidazole was administered subblastodermically at different doses with the help of a Hamilton microinjector. The eggs, which were incubated again, were opened at the end of the 48th hour and evaluated macroscopically and microscopically. The effects of different doses of metronidazole injection on neural tube development were investigated and the findings were analyzed. While 22 embryos were examined in the control group, 24, 23, 24 embryos were examined in the low dose, medium dose and high dose groups, respectively. The morphological characteristics of the embryos, whether the neural tube was open or closed, fore-aft lengths, embryological developments and somite numbers were examined under a light microscope and a stereo microscope. The data obtained were presented in tables with statistical analysis. It was determined that the neural tube was closed in 18 embryos (72%) in the control group, the neural tube was open in 4 embryos (16%), and developmental delay was detected in 3 embryos (12%). In the group injected with low dose metronidazole, the neural tube was observed to be closed in 16 embryos (64%), the neural tube was open in 8 embryos (32%), and developmental delay was observed in 1 embryo (4%). In the group injected with medium dose metronidazole, the neural tube was found to be closed in 16 embryos (64%), the neural tube was open in 7 embryos (28%), and developmental delay was detected in 2 embryos (8%). In the group injected with high doses of metronidazole, the neural tube was observed to be closed in 14 embryos (56%), the neural tube was open in 9 embryos (36%), and developmental delay was observed in 2 embryos (8%). These findings suggest that increasing metronidazole dosage may affect neural tube closure. In the control group, the average value of fore-aft length was measured as 6.28 ± 0.28 mm and the average number of somites was determined as 18.20 ± 0.73. In addition, it was determined that the embryos were between stages 11 and 13 according to the Hamburger Hamilton scale. Secondly, for the low dose group examined, the fore-and-aft length was measured as 6.98 ± 0.14 mm on average, and the number of somites was measured as 20.40 ± 0.61 on average. The embryos are 11-12 on the Hamburger Hamilton scale. It was determined that it was in the phase Thirdly, for the medium dose group examined, the average fore-and-aft length was found to be 6.46 ± 0.09 mm, and the average number of somites was 19.40 ± 0.66. The embryos are 11-12 on the Hamburger Hamilton scale. It was observed that it was in the range of stages. Fourthly, for the high dose group examined, the average fore-aft length was determined as 6.35 ± 0.23 mm, and the average number of somites was 17.81 ± 0.68. The embryo is 11-12 on the Hamburger Hamilton scale. It was found to be in the stage range. According to the data, there was no statistically significant difference between the experimental groups and the control group in terms of somite number and fore-aft lengths (p>0.05). These results showed that metronidazole had no effect on embryo development or somite number at the indicated doses. Keywords: Chick Embryo Model, Neural Tube, Central Nervous System, Metronidazole