Human chorionic gonadotropin inhibits locomotion but not food intake independently of the area postrema and the nucleus tractus solitarius in female mice.

The nausea and vomiting of pregnancy (NVP) affect many pregnant women's quality of life, and the underlying mechanisms are still unclear. Human chorionic gonadotropin (hCG) is suspected to be a factor in exacerbating NVP due to its synchronized elevation with NVP episodes and the receptor expression in the area postrema (AP) and the nucleus tractus solitarius (NTS), which are brain regions known to regulate nausea and vomiting. However, the correlation between hCG and NVP remains inconsistent in human epidemiological studies. To elucidate the causal relationship between hCG and NVP, we evaluated the effect of hCG in mice. We found that the hCG administration suppressed locomotion without affecting food intake in intact mice, which may reflect malaise observed in NVP. Similar effects were observed in ovariectomized females, indicating that the effect is independent of sex steroids released from the ovary. Furthermore, hCG did not increase the c-Fos expression in AP or NTS, and the lesion of AP and the intermediate dorsal part of NTS did not affect the hCG-induced hypoactivity. These results suggest that locomotion suppression by hCG is independent of AP and NTS. While species differences must be considered, this research provides valuable insights into the potential role of hCG in NVP.