Effect of chronic hypoxia on autonomic nervous system of fetal mice

The aim of this study is to investigate how chronic hypoxia could affect the autonomic nervous system in fetal mouse (at gestational day 17.5) by using an invasive Fetal Electrocardiography (FECG) technique. Total of 33 pregnant female mice were divided into two groups (sham control (N=13) and chronic hypoxia (N=20)). In chronic hypoxia mice at day 15.5, ligations were placed around the uterine vessels that were tied with nylon thread 0.5 mm in diameter to induce partially chronic hypoxia. Sham mice were operated on in a fashion similarly but without ligation. On 17.5-day beat-to-beat heart intervals were measured for 20 minutes by using an invasive FECG techniques inserting two needle electrodes and a ground. Results show that tone decreases when entropy increases in sham group. On the other hand in chronic hypoxia group tone increases when entropy increases. Therefore, effect of chronic hypoxia is shown to have more pronounced on tone values in the higher range of entropy values (4.2~6.0). Differences in hypoxic effect on individual fetal mice might represent the differences in maturating sympathetic nervous system because chronic hypoxia induces more sympathetic influences in fetal mice.