Human chorionic gonadotropin reduces proliferation but not survival of BrdU-labeled cells in the dentate gyrus in a rat model of pregnancy

Human chorionic gonadotropin (hCG) and luteinizing hormone (LH) are proluteotropic hormones that signal via a common receptor (LH/CG receptor), which is expressed throughout the brain. hCG has also been linked to changes in cognition during human pregnancy, and to parallel behavioural effects in rat models. Additionally, LH treatment increases cell proliferation in the dentate gyrus in some non-pregnancy rat models. This suggests a possible role for hCG in regulating neurogenesis during pregnancy. To test this hypothesis, ovariectomized rats were implanted with silastic capsules to mimic the levels of estrogen and progesterone present in early pregnancy, and injected with BrdU to label dividing cells. Treatment with hCG resulted in significantly lowered cell proliferation in the dentate gyrus, but had no impact on 21 day cell survival. These results also suggest a mechanism underlying the relationship between hCG levels and changes in cognition during pregnancy.