 The coroid plexus, CP, is a part of the brain that secretes molecules into the cerebrospinal fluid, CSF. This research has found that these molecules are affected by circadian rhythms which are controlled by the body's internal clock. The researchers used a variety of techniques to study how the CP and CSF changed throughout the day, including ribosome profiling, metabolomics, and blood CSF barrier analysis. They found that the CP and CSF have different metabolite profiles depending on the time of day, as well as changes in cellular junctions and thyroid hormones. Additionally, they were able to track the movement of thyroid hormones from the CP to the CSF using a special mouse model. This research provides insight into how the CP and CSF work together to regulate brain states and could lead to new treatment for disorders such as depression or anxiety. This article was authored by Ryan M. Fame, Peter N. Callagin, Boreanna Petrova, and others.